Solar cell and method for manufacturing solar cell

Abstract

The invention relates to the technical field of semiconductors, in particular to a solar cell and a preparation method of the solar cell. The solar cell comprises a cell substrate, an In reduction layer and electroplating grid lines, wherein the cell substrate comprises a transparent conductive layer with a microporous structure; the In reduction layer is formed in the area, with the micropore structure, of the transparent conducting layer; an electroplating grid line is formed on the In reduction layer; the preparation method comprises the following steps: coating, printing and developing a battery substrate; pretreating the transparent conductive layer of the battery substrate to form a microporous structure; in reduction is carried out, so that an In reduction layer is formed in the area, where the micropore structure is formed, of the transparent conductive layer. And electroplating to form an electroplating grid line on the In reduction layer. According to the preparation method, the arrangement of the copper seed layer can be reduced, the preparation cost can be reduced, the problem of grid breakage of the solar cell prepared by the method is not easy to occur, the good conductivity of the solar cell is ensured, the reliability of the solar cell is improved, and the service life of the solar cell is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and in particular, to a solar cell and a preparation method of the solar cell. BACKGROUND

[0002] With the development of photovoltaic technology, the advantages of N-type cells are becoming more and more obvious; TOPCon and HJT are two important representatives.

[0003] Among them, the heterojunction cell (HJT) has multiple advantages such as high conversion efficiency and simple process structure. In the preparation method of the traditional heterojunction cell, a silver paste is usually printed on both sides to form a silver grid line on the surface of the TCO conductive film. Due to the high cost of silver paste, in order to reduce costs and increase efficiency, some related technologies use copper interconnection to form a copper grid line on the TCO conductive film to replace the silver grid line printed by screen printing. The copper interconnection method includes: first, depositing a copper seed layer on the TCO film by PVD sputtering to conduct electricity using the copper seed layer, then coating and printing, then transferring the pattern by developing, then edging and electroplating to form a copper grid line by electroplating, then removing the film and etching to remove the non-grid line area of the film and the copper seed layer, and finally using a chemical tin plating method to plate a protective tin layer.

[0004] However, the copper interconnection technology needs to set a copper seed layer first, so the effect of reducing costs is limited; if the copper seed layer is removed, it is easy to cause the grid to break and will adversely affect the conductivity of the solar cell and reduce the reliability and life of the solar cell. SUMMARY

[0005] The purpose of the present application includes providing a solar cell and a preparation method of the solar cell. The preparation method of the solar cell of the present application can reduce the setting of the copper seed layer, which is beneficial to reduce the preparation cost, and the solar cell prepared by the method is not prone to the problem of grid breakage, which is beneficial to ensure the good conductivity of the solar cell and improve the reliability and life of the solar cell.

[0006] Embodiments of the present application can be implemented as follows: In a first aspect, the present application provides a solar cell, comprising: a cell substrate, the cell substrate comprising a transparent conductive layer, the transparent conductive layer being formed with a microporous structure; an In reduction layer, the In reduction layer being formed in the region where the transparent conductive layer is formed with a microporous structure; and an electroplated grid line, the electroplated grid line being formed on the In reduction layer.

[0007] In an optional embodiment, the thickness of the region where the transparent conductive layer is formed with a microporous structure is 10-20 nm.

[0008] In optional embodiments, the battery substrate has a front surface and a back surface, and both the front surface and the back surface comprise a transparent conductive layer; and / or, The electroplated grid line comprises at least two layers of copper layers with different deposition densities arranged in a stack.

[0009] In a second aspect, the present application provides a method for preparing a solar cell, for preparing the solar cell of any one of the preceding embodiments; the method for preparing a solar cell comprises: coating, printing, and developing the battery substrate; pre-treating the transparent conductive layer of the battery substrate to form a microporous structure; In reduction, to form an In reduction layer in the area of the transparent conductive layer with the microporous structure; and, electroplating, to form an electroplated grid line in the In reduction layer.

[0010] In optional embodiments, the step of pre-treating comprises etching the transparent conductive layer with a mixture of fluosilicic acid and nitric acid.

[0011] In optional embodiments, the fluosilicic acid has a volume concentration of 0.5±0.1%, the nitric acid has a volume concentration of 3±0.5%, and the volume ratio of the fluosilicic acid and the nitric acid is 1:1; and / or, The etching temperature is 25-40℃, and the etching time is 30-60s.

[0012] In optional embodiments, the electroplating solution for electroplating comprises 2-8g / L polyethylene glycol, 1-5g / L thiourea, and 0.1-0.5g / L nano silicon carbide particles.

[0013] In optional embodiments, the electroplating comprises pre-plating and main electroplating; wherein the current density of the pre-plating is less than the current density of the main electroplating.

[0014] In optional embodiments, the current density of the pre-plating is 1-3A / dm 2 , and the current density of the main electroplating is 4-6 A / dm 2 ; and / or, The pre-plating time is 10-30s, and the main electroplating time is 7±2min.

[0015] In optional embodiments, the step of In reduction comprises reducing the battery substrate with a neutral chloride system electrolyte containing In ions; wherein the current density of the In reduction is 50-200 A / m 2 , the temperature is 25-50℃, and the voltage is 1.5-3.0V.

[0016] The solar cell provided by the embodiment of the present application has the beneficial effects that the mechanical interlocking effect is formed between the microporous structure formed in the transparent conductive layer and the subsequently formed electroplated grid lines, so that the binding stability of the electroplated grid lines is improved, the problem of broken grid is effectively solved, the good conductivity of the solar cell is ensured, and the reliability and service life of the solar cell are improved.

[0017] The method for preparing the solar cell provided by the embodiment of the present application has the beneficial effects that the copper seed layer is not needed to be arranged, so that the preparation cost is reduced; meanwhile, the microporous structure is formed by pretreating the transparent conductive layer of the cell substrate, the mechanical interlocking effect is formed between the microporous structure and the subsequently formed electroplated grid lines, so that the binding stability of the electroplated grid lines is improved, the problem of broken grid is effectively solved, the good conductivity of the solar cell is ensured, and the reliability and service life of the solar cell are improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0019] Figure 1 It is a structural schematic diagram of the solar cell in the present application; Figure 2 It is a scanning electron microscope image of the microporous structure of the transparent conductive layer in the embodiment 1 of the present application; Figure 3 It is a scanning electron microscope image of the microporous structure of the transparent conductive layer in the comparative example 1 of the present application.

[0020] Figure: 010-solar cell; 100-cell substrate; 110-substrate; 120-intrinsic amorphous silicon layer; 131-N-type doped layer; 132-P-type doped layer; 140-transparent conductive layer; 200-In reduction layer; 300-electroplated grid lines. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the application provided in the drawings is not intended to limit the scope of the application claimed, but merely represents selected embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the application.

[0023] It should be noted that similar reference numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it need not be further defined and explained in subsequent drawings.

[0024] In the description of the application, it should be noted that if the terms "upper", "lower", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed, and are only for the convenience of describing the application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application.

[0025] In addition, if the terms "first", "second" and the like appear, they are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0026] It should be noted that the features in the embodiments of the application can be combined with each other without conflict.

[0027] The copper interconnection technology provided by the related art includes forming a copper grid line on a TCO conductive film to replace a screen-printed silver grid line. The method of copper interconnection includes first depositing a copper seed layer on the TCO film by PVD sputtering to conduct electricity using the copper seed layer, then coating and printing, then achieving pattern transfer by developing, then edging and electroplating to form a copper grid line by electroplating, then removing the film and etching to remove the adhesive film and copper seed layer in the non-grid line area, and finally using a chemical tin plating method to plate a protective tin layer.

[0028] Although the copper interconnection electroplating grid line process can reduce some costs compared to printing a silver grid line, the effect of reducing costs is limited. If the copper seed layer is removed, the cost can be further reduced. However, the inventor has found that removing the copper seed layer causes interface defects, chemical reactions and mechanical stress problems, which easily lead to a decrease in the bonding strength of the grid line, i.e., the phenomenon of broken grid lines easily occurs, which adversely affects the conductivity of the solar cell and reduces the reliability and life of the solar cell.

[0029] To improve the above problems, please refer to Figure 1The solar cell 010 provided by the present disclosure comprises a cell substrate 100, an In reduction layer 200 and a plated grid line 300, the cell substrate 100 comprises a transparent conductive layer 140, the transparent conductive layer 140 is formed with a microporous structure; the In reduction layer 200 is formed in the area where the transparent conductive layer 140 is formed with the microporous structure; and the plated grid line 300 is formed on the In reduction layer 200.

[0030] By forming the mechanical interlocking effect between the microporous structure of the transparent conductive layer 140 and the subsequently formed plated grid line 300, the bonding stability of the plated grid line 300 is improved, the problem of broken grid is effectively improved, which is conducive to ensuring the good conductivity of the solar cell 010 and improving the reliability and service life of the solar cell 010.

[0031] It should be noted that the solar cell 010 provided by the present disclosure can be a heterojunction cell.

[0032] Optionally, the cell substrate 100 has a front surface and a back surface, both the front surface and the back surface comprise the transparent conductive layer 140, and the transparent conductive layer 140 of the front surface and the back surface is formed with a microporous structure.

[0033] Optionally, the area of the transparent conductive layer 140 formed with the microporous structure has a thickness of 10-20 nm, for example, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, etc., which is not limited herein.

[0034] Optionally, the microporous structure can comprise pores with a pore size of 0.1-50 microns (μm), and / or pores with a pore size of 1-100 nanometers (nm), and / or pores with a pore size of 50 μm-1 mm.

[0035] Optionally, the microporous structure only comprises pores with a pore size of less than 2 nm.

[0036] Optionally, the front surface and the back surface of the cell substrate 100 are both formed with the In reduction layer 200, that is, the area of the microporous structure of the transparent conductive layer 140 of the front surface and the back surface is formed with the In reduction layer 200.

[0037] Optionally, the In reduction layer 200 of the front surface and the back surface of the cell substrate 100 is provided with the plated grid line 300.

[0038] Optionally, the plated grid line 300 comprises at least two layers of copper layers which are arranged in a stack and have different deposition densities.

[0039] Optionally, the battery base 100 comprises a substrate 110, an intrinsic amorphous silicon layer 120, an N-type doped layer 131, an ITO layer (i.e., a transparent conductive layer 140 on the front side) arranged in sequence on the front side of the substrate 110, and an intrinsic amorphous silicon layer 120, a P-type doped layer 132 and an ITO layer (i.e., a transparent conductive layer 140 on the back side) arranged in sequence on the back side of the substrate 110.

[0040] Optionally, the substrate 110 is an N-type silicon wafer.

[0041] The present disclosure also provides a preparation method of the above-mentioned solar cell 010, which comprises: coating, printing, developing and edge covering the battery base 100 (i.e., a blue film sheet commonly known as); preprocessing the transparent conductive layer 140 of the battery base 100 to form a microporous structure; forming an In reduction layer 200 on the area of the transparent conductive layer 140 where the microporous structure is formed by In reduction; and, electroplating to form an electroplated grid line 300 on the In reduction layer 200; film removal, light injection and tin conversion.

[0042] The preparation method of the solar cell 010 does not need to set a copper seed layer, so that the preparation cost can be reduced; at the same time, by preprocessing the transparent conductive layer 140 of the battery base 100 to form a microporous structure, a mechanical interlocking effect can be formed between the microporous structure and the subsequently formed electroplated grid line 300, so as to improve the bonding stability of the electroplated grid line 300, effectively improve the problem of broken grid, and be conducive to ensuring the good conductivity of the solar cell 010 and improving the reliability and service life of the solar cell 010.

[0043] Optionally, the preprocessing step comprises etching the transparent conductive layer 140 with a mixture of fluosilicic acid and nitric acid. The etching method is simple, easy to operate, and facilitates the reliable formation of the microporous structure.

[0044] Optionally, in the etching solution for preprocessing, the volume concentration of fluosilicic acid (H2SiF6) is 0.5±0.1% (for example: 0.4%, 0.5%, 0.6%, etc., which is not specifically limited here), the volume concentration of nitric acid (HNO3) is 3±0.5% (for example: 2.5%, 2.8%, 3.0%, 3.3%, 3.5%, etc., which is not specifically limited here), and the volume ratio of fluosilicic acid to nitric acid is 1:1. Optimizing the ratio of fluosilicic acid to nitric acid can not only reliably form a microporous structure on the transparent conductive layer 140, but also improve the etching efficiency and reduce the introduction of other impurities to ensure the good electrical performance of the solar cell 010.

[0045] Optionally, the etching temperature is 25-40℃ (for example: 25℃, 30℃, 35℃, 40℃, etc., which are not limited herein), and the etching time is 30-60s (for example: 30s, 40s, 50s, 60s, etc., which are not limited herein). The optimized etching temperature and time can ensure the efficiency of the pretreatment and the controllability of the shape and thickness of the microporous structure formed by etching, ensure that the depth of the microporous structure formed on the transparent conductive layer 140 is 10-20nm, and further ensure that the subsequently formed plated grid lines 300 can reliably form a mechanical interlocking effect with the microporous structure, improve the grid breaking phenomenon, and improve the problem of excessive etching, i.e., the problem of excessive (excessive thickness) microporous structure formed.

[0046] Optionally, the In reduction step includes reducing the battery substrate 100 with a neutral chloride system electrolyte containing In ions; wherein the mass concentration of the electrolyte is 50-100g / L, for example: 50g / L, 60g / L, 70g / L, 80g / L, 90g / L, 100g / L, etc., which are not limited herein.

[0047] Optionally, the neutral chloride system electrolyte containing In ions includes an indium chloride solution.

[0048] Optionally, the current density of the In reduction is 50-200 A / m 2 (for example: 50A / m 2 , 70 A / m 2 , 100 A / m 2 , 120A / m 2 , 150 A / m 2 , 180 A / m 2 , 200 A / m 2 , etc., which are not limited herein), the temperature is 25-50℃ (for example: 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, etc., which are not limited herein), and the voltage is 1.5-3.0V (for example: 1.5V, 1.8V, 2.0V, 2.2V, 2.5V, 2.7V, 3.0V, etc., which are not limited herein).

[0049] When reducing In, a too low current density will result in low efficiency, and a too high current density will form a loose deposition layer; therefore, in order to improve the above problems, when reducing the battery substrate 100 in the electrolyte system, the current density is controlled to be 50-200 A / m 2 .

[0050] When reducing In, a too high temperature will accelerate undesirable side reactions; in order to reduce the side reaction speed, when reducing the battery substrate 100 in the electrolyte system, the temperature is controlled to be 25-50℃.

[0051] Optionally, the time for In reduction is 40-60s, for example, 40s, 45s, 50s, 55s, 60s, etc., which is not limited herein.

[0052] Optionally, when In reduction is performed in an electrolyte system, mechanical stirring or air stirring can be performed in the electrolytic cell to ensure uniform separation of ion concentration in the electrolyte and reduce concentration difference polarization.

[0053] Optionally, the method for In reduction further comprises using stainless steel, titanium metal (such as titanium plate) or platinum-coated titanium metal (such as platinum-coated titanium mesh) as the cathode, which is conducive to ensuring the cleanliness of the surface and improving the adhesion of the In reduction layer 200; and using inert materials as the anode, for example, platinum, graphite or titanium-coated IrO2 / Ta2O5 DSA anode, which can improve the problem of anode dissolution and contamination of the electrolyte.

[0054] It should be noted that when In reduction is performed in an electrolyte system, the electrochemical reactions involved include: Cathode reaction: In 3+ + 3e - → In (main reaction); Anode reaction: 4OH - → O2↑ + 2H2O + 4e - (neutral system).

[0055] Optionally, after the In reduction layer 200 is formed, cleaning (for example, rinsing the cathode deposit with deionized water to remove residual electrolyte) and drying (for example, drying under vacuum or inert atmosphere to prevent oxidation) can be performed.

[0056] Optionally, the method for forming the electroplated grid line 300 is gradient electroplating deposition; wherein the electroplating includes pre-plating and main electroplating; wherein the current density of the pre-plating is less than that of the main electroplating. Pre-plating at a smaller current density can promote uniform nucleation of copper crystal nuclei; main electroplating at a higher current density can increase the deposition speed; and the use of gradient electroplating can effectively form at least two copper layers that are stacked and have different deposition densities.

[0057] Optionally, the current density of the pre-plating is 1-3 A / dm 2 (for example, 1 A / dm 2 , 1.5 A / dm 2 , 2 A / dm 2 , 2.5 A / dm 2 , 3 A / dm 2etc., which are not specifically limited herein). The current density of the main plating is 4-6 A / dm 2 (For example: 4 A / dm 2 , 4.5 A / dm 2 , 5 A / dm 2 , 5.5 A / dm 2 , 6 A / dm 2 etc., which are not specifically limited herein).

[0058] Optionally, the pre-plating time is 10-30 s (for example: 10 s, 15 s, 20 s, 25 s, 30 s, etc., which are not specifically limited herein), and the main plating time is 7±2 min (for example: 5 min, 6 min, 7 min, 8 min, 9 min, etc., which are not specifically limited herein).

[0059] Optionally, the plating solution includes 2-8 g / L polyethylene glycol (for example: 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, etc., which are not specifically limited herein), 1-5 g / L thiourea (for example: 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, etc., which are not specifically limited herein), and 0.1-0.5 g / L nano silicon carbide particles (for example: 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, etc., which are not specifically limited herein). The PEG in the electrolyte can inhibit dendrite growth, the thiourea can refine the grains, and the nano SiC can enhance the interface bonding. Through the synergistic effect of the raw materials of the electrolyte, the internal stress of the plated grid line 300 can be reduced, so as to reliably improve the bonding force between the plated copper grid line and the transparent conductive layer 140, and effectively improve the grid breakage problem caused by the absence of a seed layer.

[0060] Optionally, the particle size of the nano silicon carbide particles can be 10-200 nm.

[0061] Embodiment 1 Preparation of a solar cell: 1. Coating on the cell substrate (i.e., a blue film sheet).

[0062] 2. Printing.

[0063] 3. Developing and edge wrapping.

[0064] 4. Preprocessing the transparent conductive layer (i.e., the ITO layer) of the cell substrate with an etching solution to form a microporous structure; wherein the etching solution includes fluorosilicic acid (volume concentration of 0.5%) and nitric acid (volume concentration of 3%) in a volume ratio of 1:1, the etching temperature is 25°C, and the time is 60 s.

[0065] 5、In reduction, In reduction layer is formed in the area where the transparent conductive layer has microporous structure. Specifically, In reduction is performed on the battery substrate in a neutral electrolyte system. In the process, the electrolyte is InCl3 solution with mass concentration of 50 g / L; the cathode electrode is stainless steel and the anode electrode is platinum; the current density is 50 A / m 2 , the temperature is 50℃ and the voltage is 1.5V; after the In reduction layer is formed, the battery substrate is cleaned and dried.

[0066] 6、Electroplating, to form electroplated grid lines on the In reduction layer. Specifically, the electroplating solution used in the electroplating contains 8 g / L polyethylene glycol (PEG), 1 g / L thiourea and 0.3 g / L nano silicon carbide particles; the electroplating includes pre-plating and main electroplating, in which the current density for pre-plating is 3 A / dm 2 , and after 10 seconds of pre-plating, the current density is switched to 6 A / dm 2 for main electroplating, and the main electroplating is performed for 7 minutes, so as to form the layered copper structure.

[0067] 7、Film removal, photo injection, tin conversion.

[0068] The prepared solar cell has microporous structure (as shown in Figure 2 ) in the transparent conductive layer, and the electroplated copper grid lines are formed on the In reduction layer in the area where the microporous structure is located in the transparent conductive layer; the thickness of the area where the microporous structure is located is 15 nm.

[0069] Example 2 Preparation of a solar cell: 1、Coating on the battery substrate (i.e., a blue film sheet).

[0070] 2、Printing.

[0071] 3、Developing and edge wrapping.

[0072] 4、Pretreatment of the transparent conductive layer of the battery substrate with etching solution to form microporous structure; the etching solution includes fluorosilicic acid (volume concentration of 0.4%) and nitric acid (volume concentration of 3.5%) in a volume ratio of 1:1, the etching temperature is 40℃ and the etching time is 30 seconds.

[0073] 5、In reduction, In reduction layer is formed in the area where the transparent conductive layer has microporous structure. Specifically, In reduction is performed on the battery substrate in a neutral electrolyte system. In the process, the electrolyte is InCl3 solution with mass concentration of 50 g / L; the cathode electrode is stainless steel and the anode electrode is platinum; the current density is 50 A / m 2 , the temperature is 50℃ and the voltage is 1.5V; after the In reduction layer is formed, the battery substrate is cleaned and dried.

[0074] 6. Electroplating to form electroplated grid lines on the In reduction layer. Specifically, the electroplating uses an electroplating solution containing 2 g / L polyethylene glycol (PEG), 5 g / L thiourea and 0.1 g / L nano silicon carbide particles; the electroplating includes pre-plating and main electroplating, wherein the current density of pre-plating is 1 A / dm 2 , and after 30 s of pre-plating, the current density is switched to 4 A / dm 2 for main electroplating, and the time of main electroplating is 9 min, so as to form a layered copper structure.

[0075] 7. Film removal, photo injection, tin conversion.

[0076] The prepared solar cell has a transparent conductive layer formed with a microporous structure, and the electroplated copper grid lines are formed on the In reduction layer located in the microporous structure region of the transparent conductive layer; wherein the thickness of the microporous structure region is 20 nm.

[0077] Example 3 Preparation of a solar cell: 1. Coating on a cell substrate (i.e., a blue film sheet).

[0078] 2. Printing.

[0079] 3. Developing, and edge wrapping.

[0080] 4. Pre-treating the transparent conductive layer of the cell substrate with an etching solution to form a microporous structure; wherein the etching solution includes fluorosilicic acid (volume concentration of 0.6%) and nitric acid (volume concentration of 2.5%) in a volume ratio of 1:1, the etching temperature is 30°C, and the time is 45 s.

[0081] 5. In reduction, to form an In reduction layer in the region of the transparent conductive layer formed with a microporous structure. Specifically, In reduction is performed on the cell substrate in a neutral electrolyte system. Wherein the electrolyte is an InCl3 solution with a mass concentration of 80 g / L; the cathode electrode is a platinized titanium mesh, and the anode electrode is a DSA coated with IrO2 / Ta2O5 on titanium; the current density is 100 A / m 2 , the temperature is 45°C, and the voltage is 2.0 V; after forming the In reduction layer, cleaning and drying are performed.

[0082] 6. Electroplating to form electroplated grid lines on the In reduction layer. Specifically, the electroplating uses an electroplating solution containing 2 g / L polyethylene glycol (PEG), 5 g / L thiourea and 0.1 g / L nano silicon carbide particles; the electroplating includes pre-plating and main electroplating, wherein the current density of pre-plating is 1 A / dm 2 , and after 30 s of pre-plating, the current density is switched to 4 A / dm 2 for main electroplating, and the time of main electroplating is 9 min, so as to form a layered copper structure.

[0083] 7. Stripping, photo-injection, tin reduction.

[0084] The prepared solar cell has a transparent conductive layer with a microporous structure, and the plated copper grid lines are formed on the In reduction layer in the area of the microporous structure of the transparent conductive layer; wherein the thickness of the area of the microporous structure is 10 nm.

[0085] Comparative Example 1 Comparative Example 1 differs from Example 1 in that the transparent conductive layer (i.e., ITO layer) is not pretreated, but is directly reduced to form an In reduction layer, and the grid lines are plated; other process parameters refer to Example 1.

[0086] Please refer to Figure 3 The transparent conductive layer of Comparative Example 1 does not have a microporous structure.

[0087] The number of broken grids of Example 1 and Comparative Example 1 with a repetition number of 100 is counted, and the broken grid ratio results are shown in Table 1.

[0088] Table 1

[0089] According to the results in Table 1, by pretreating the transparent conductive layer to form a microporous structure, the broken grid ratio can be effectively reduced, which shows that the pretreatment of the transparent conductive layer has obvious improvement on the broken grid of the heterojunction seed layer-free plated cell.

[0090] Comparative Example 2 Comparative Example 2 differs from Example 1 in that the volume concentration of fluosilicic acid in step 4 is 1%, and the volume concentration of nitric acid is 2%; other process parameters refer to Example 1.

[0091] Comparative Example 3 Comparative Example 3 differs from Example 1 in that the plating step in step 6 is not gradient plating, but only plating under the condition of a current density of 6 A / dm 2 ; other process parameters refer to Example 1.

[0092] Comparative Example 4 Comparative Example 4 differs from Example 1 in that the volume concentration of fluosilicic acid in step 4 is 1%, and the volume concentration of nitric acid is 2%; the plating step in step 6 is not gradient plating, but only plating under the condition of a current density of 6 A / dm 2 ; other process parameters refer to Example 1.

[0093] The number of broken grids of Example 1 and Comparative Examples 2, 3, and 4 with a repetition number of 100 is counted, and the broken grid ratio results are shown in Table 2.

[0094] Table 2

[0095] According to Table 2, comparing Example 1 and Comparative Example 2, when etching the transparent conductive layer, if the volume concentration of fluosilicic acid and nitric acid is low, the micro-porous structure formed on the transparent conductive layer is less, and thus it is difficult to improve the adhesion of the plated grid line while reducing the copper seed layer, resulting in an increase in the proportion of broken grid.

[0096] Comparing Example 1 and Comparative Example 3, when plating the grid line, if gradient plating is not used (i.e., without pre-plating under a small current density condition and then plating under a large current density), even if sufficient micro-porous structure is formed on the transparent conductive layer, the adhesion of the plated grid line cannot be improved, resulting in an increase in the proportion of broken grid.

[0097] Comparing Example 1 and Comparative Examples 2-4, using a suitable treatment agent to etch and pretreat the transparent conductive layer to obtain sufficient micro-porous structure, and in combination with gradient plating (i.e., pre-plating under a small current density condition and then plating under a large current density), can reliably improve the adhesion of the plated grid line while reducing the copper seed layer, and sufficiently reduce the proportion of broken grid.

[0098] In summary, the preparation method of the solar cell 010 of the present application can reduce the setting of the copper seed layer, which is conducive to reducing the preparation cost, and the solar cell 010 prepared by the method is not prone to the problem of broken grid, which is conducive to ensuring the good conductivity of the solar cell 010 and improving the reliability and life of the solar cell 010.

[0099] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements within the technical range disclosed by the present application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the present application.

Claims

1. A solar cell, characterized by, The solar cell comprises: a battery substrate (100) comprising a transparent conductive layer (140) formed with a microporous structure; an In reduction layer (200) formed on the area of the transparent conductive layer (140) formed with the microporous structure; and a plated grid line (300) formed on the In reduction layer (200).

2. The solar cell according to claim 1, characterized in that, The area of the transparent conductive layer (140) formed with the microporous structure has a thickness of 10-20 nm.

3. The solar cell according to claim 1, characterized in that, The battery substrate (100) has a front surface and a back surface, both of which comprise the transparent conductive layer (140); and / or The plated grid line (300) comprises at least two layers of copper layers with different deposition densities arranged in a stack.

4. A method for producing a solar cell, characterized by, The solar cell of any one of claims 1-3 is prepared by a method comprising: coating, printing and developing the battery substrate (100); preprocessing the transparent conductive layer (140) of the battery substrate (100) to form a microporous structure; In reduction to form an In reduction layer (200) on the area of the transparent conductive layer (140) formed with the microporous structure; and plating to form a plated grid line (300) on the In reduction layer (200).

5. The method of producing a solar cell according to claim 4, wherein The preprocessing step comprises etching the transparent conductive layer (140) with a mixture of fluosilicic acid and nitric acid.

6. The method of producing a solar cell according to claim 5, wherein The fluosilicic acid has a volume concentration of 0.5±0.1%, the nitric acid has a volume concentration of 3±0.5%, and the volume ratio of the fluosilicic acid to the nitric acid is 1:1; and / or The etching is performed at a temperature of 25-40℃ for 30-60 s.

7. The method of producing a solar cell according to claim 4, wherein The plating solution for the plating comprises 2-8 g / L polyethylene glycol, 1-5 g / L thiourea, and 0.1-0.5 g / L nano silicon carbide particles.

8. The method of producing a solar cell according to any one of claims 4 to 7, wherein The plating comprises pre-plating and main plating; wherein the current density of the pre-plating is less than that of the main plating.

9. The method of producing a solar cell according to claim 8, characterized by, The current density of the pre-plating is 1-3 A / dm2, and the current density of the main plating is 4-6 A / dm2; and / or The pre-plating is performed for 10-30 s, and the main plating is performed for 7±2 min.

10. The method of producing a solar cell according to claim 4, wherein The In reduction step comprises reducing the battery substrate (100) with a neutral chloride system electrolyte containing In ions; wherein the current density of the In reduction is 50-200 A / m2, the temperature is 25-50℃, and the voltage is 1.5-3.0 V.

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