Electrodeposition method of metal grid line and metal grid line

Abstract

The embodiment of the present disclosure provides a method for electrodeposition of metal grid lines and metal grid lines, which relate to the field of photovoltaic manufacturing technology. The method comprises: pouring a mixture of polydimethylsiloxane prepolymer and curing agent on an original template, curing and forming after removing all bubbles, and demolding after cooling to room temperature to obtain a core mold with a grid line structure; placing the core mold in a chemical metal plating solution, stirring and reacting at room temperature to deposit a metal conductive layer on the surface of the core mold; irradiating the core mold with the metal conductive layer deposited on the surface with ultraviolet light to change the wettability of the core mold surface from hydrophobic to super-hydrophilic; laminating the super-hydrophilic core mold with a silicon substrate, and immersing it in an electroplating solution as a cathode for electrodeposition to form a metal grid line structure; performing low-temperature heat treatment on the core mold after electrodeposition to achieve super-hydrophobic conversion of the wettability of the core mold surface; taking out the metal grid line structure from the super-hydrophobic core mold to obtain the metal grid line. The present disclosure can improve stability.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the field of photovoltaic power generation technology, and in particular to a method for electro-deposition of a metal grid line and a metal grid line. Background Art

[0002] Metal grid lines can collect the current generated by solar cells and transmit it to external circuits. With the development of photovoltaic technology, traditional screen printing technology is difficult to meet the requirements of high-performance solar cells for low line width and low cost of metal grid lines. Electroplating technology has gradually become the main method for preparing metal grid lines. However, the process of electroplating metal grid lines has problems such as high cost of graphic process, low efficiency of electrodeposition and difficulty in post-processing and degumming.

[0003] In view of the above problems, the problems in the process of electroplating metal grid lines can be solved by regulating the hydrophilicity and hydrophobicity of the core mold surface. In the related art, the methods for regulating the hydrophilicity and hydrophobicity of the core mold surface mainly include chemical modification, plasma treatment, self-assembled monolayer film, etc. The above methods have problems such as complex process, high cost, and poor stability. Summary of the invention

[0004] The purpose of the present disclosure is to provide a method for electroplating a metal grid line and a metal grid line, thereby at least to a certain extent overcoming the problems of complex process, high cost and poor stability in regulating the hydrophobicity of the core mold surface due to the limitations and defects of the relevant technology.

[0005] According to one aspect of the present disclosure, a method for electroplating a metal grid line is provided, comprising: pouring a mixture of a polydimethylsiloxane prepolymer and a curing agent on an original template having a grid line pattern, curing and forming the mixture after removing all bubbles, and demolding the mixture after cooling to room temperature to obtain a polydimethylsiloxane core mold with a grid line structure; placing the polydimethylsiloxane core mold in a chemical metal plating solution, stirring the reaction at room temperature to deposit a metal conductive layer on the surface of the polydimethylsiloxane core mold to obtain a metal grid line structure; and depositing a metal conductive layer on the surface of the polydimethylsiloxane core mold to obtain a metal grid line structure. The polydimethylsiloxane core mold with a metal conductive layer is irradiated with ultraviolet light to change the wettability of the surface of the polydimethylsiloxane core mold from hydrophobic to super-hydrophilic; the super-hydrophilic polydimethylsiloxane core mold is bonded to a silicon substrate and immersed in a plating solution as a cathode for electrodeposition; the polydimethylsiloxane core mold after electrodeposition is subjected to low-temperature heat treatment to achieve super-hydrophobic conversion of the wettability of the surface of the polydimethylsiloxane core mold; and the metal grid line structure is removed from the super-hydrophobic polydimethylsiloxane core mold to obtain the metal grid line.

[0006] In an exemplary embodiment of the present disclosure, the metal conductive layer is any one of silver, nickel and copper.

[0007] In an exemplary embodiment of the present disclosure, the ultraviolet light irradiation time is 2 to 30 hours.

[0008] In an exemplary embodiment of the present disclosure, the electrodeposition includes direct current electrodeposition or pulse electrodeposition, and the current density of the electrodeposition is 1-10 A / dm 2 .

[0009] In an exemplary embodiment of the present disclosure, the temperature of the low temperature heat treatment is 100-150° C., and the time of the low temperature heat treatment is 5-60 minutes.

[0010] In an exemplary embodiment of the present disclosure, the mixing ratio of the polydimethylsiloxane prepolymer and the curing agent is 10:1.

[0011] In an exemplary embodiment of the present disclosure, the temperature of the curing process is 100°C.

[0012] In an exemplary embodiment of the present disclosure, a super-hydrophilic polydimethylsiloxane core mold is bonded to a silicon substrate and immersed in a plating solution as a cathode for electrodeposition, including: bonding the super-hydrophilic polydimethylsiloxane core mold to a conductively treated silicon substrate through a clamp, and immersing the super-hydrophilic polydimethylsiloxane core mold in a plating solution as a cathode for electrodeposition; wherein the plating solution includes one of a copper plating solution, a nickel plating solution, and a copper-nickel alloy plating solution.

[0013] In an exemplary embodiment of the present disclosure, the method further includes: when the metal gate line structure deposition reaches a target thickness, taking out the super-hydrophilic polydimethylsiloxane core mold, and immersing the super-hydrophilic polydimethylsiloxane core mold in deionized water for ultrasonic cleaning.

[0014] According to one aspect of the present disclosure, a metal gate line is provided. The metal gate line is prepared according to any one of the above-mentioned methods for electro-deposition of the metal gate line.

[0015] In the technical solution provided in the embodiment of the present disclosure, on the one hand, the wettability of the surface of the polydimethylsiloxane core mold can be changed from hydrophobic to super-hydrophilic by ultraviolet light irradiation, so as to improve the liquid phase mass transfer efficiency during the electroplating process; the wettability of the surface of the polydimethylsiloxane core mold can be converted to super-hydrophobic by low-temperature heat treatment, which can reduce the interfacial adhesion during the demolding process, and the required sample can be prepared without post-treatment and degumming, which simplifies the process of regulating the hydrophobicity of the core mold surface, reduces the cost and improves the stability, shortens the process of preparing metal grid lines, and improves the preparation efficiency. On the other hand, the metal grid lines are prepared by replacing the existing graphic process with the polydimethylsiloxane core mold, which reduces the preparation cost of the metal grid lines. On the other hand, by depositing a nano-scale metal conductive layer with reversible wettability on the surface of the polydimethylsiloxane core mold, the electroplating core mold is endowed with excellent conductivity, the current density in the microcavity is increased, the deposition efficiency and forming quality of the metal grid lines are improved, and the accuracy of the metal grid lines is improved, the stability of the metal grid lines is improved, and the quality and performance of the electroplated metal grid lines can be improved.

[0016] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0018] Figure 1 A flow chart schematically illustrates a method for electro-deposition of a metal grid line in an embodiment of the present disclosure.

[0019] Figure 2 A schematic diagram showing the preparation of metal grid lines by electroplating of metal micro-parts.

[0020] Figure 3 Schematic diagram of soft etching forming of a core mold in a method for electrodeposition of a metal gate line based on a core mold with reversible wettability control in an embodiment of the present disclosure.

[0021] Figure 4 Schematic diagram of super-hydrophilic modification of the core mold surface in an embodiment of the present disclosure.

[0022] Figure 5 Schematic diagram of the change in the water contact angle of the core mold in the embodiment of the present disclosure.

[0023] Figure 6 Schematic diagram of electrodeposition and demolding in an embodiment of the present disclosure.

[0024] Figure 7 Schematic diagram of the morphology of the metal gate line structure prepared in Example 1.

[0025] Figure 8 Schematic diagram of the morphology of the metal gate line structure prepared in Example 2.

[0026] Fig. 9 Schematic diagram of the morphology of the metal gate line structure prepared in Example 3. DETAILED DESCRIPTION

[0027] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as being limited to the examples set forth herein; on the contrary, these embodiments are provided so that the present disclosure will be more comprehensive and complete, and the concepts of the example embodiments are fully conveyed to those skilled in the art. The described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced while omitting one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known technical solutions are not shown or described in detail to avoid obscuring various aspects of the present disclosure.

[0028] The terms "a", "an", "the" and "said" used in this specification are used to indicate the presence of one or more elements / components, etc.; the terms "including" and "having" are used to express an open-ended inclusion and mean that there may be additional elements / components, etc. in addition to the listed elements / components, etc.; the terms "first" and "second" etc. are used only as labels and are not intended to limit the quantity of their objects.

[0029] Metal grid lines can collect the current generated by solar cells and transmit it to external circuits. The quality of metal grid lines can directly affect the efficiency and reliability of solar cells. With the development of photovoltaic technology, traditional screen printing technology is difficult to meet the requirements of high-performance solar cells for low line width and low cost of metal grid lines. Therefore, electroplating technology has gradually become the main method for preparing metal grid lines. However, the process of electroplating metal grid lines may have problems such as high cost of graphic process, low efficiency of electrodeposition and difficulty in post-processing and degumming.

[0030] In order to solve the above problems, regulating the hydrophilicity and hydrophobicity of the mandrel surface is an effective way. The mandrel with hydrophilic surface is conducive to accelerating the liquid phase mass transfer during the electrodeposition process and improving the efficiency and quality of electroplating; while the mandrel with hydrophobic surface can reduce the interfacial adhesion between it and the coating, eliminating the need for post-treatment to remove glue, reducing the generation of toxic waste liquid, and effectively shortening the process.

[0031] At present, the commonly used methods for regulating the hydrophilicity and hydrophobicity of the core mold surface mainly include chemical modification, plasma treatment, self-assembled monolayer film, etc. These methods can regulate the hydrophilicity and hydrophobicity of the core mold surface to a certain extent, but there are problems such as complex process, high cost, and poor stability. Therefore, exploring a simple, efficient, and stable method for regulating the hydrophilicity and hydrophobicity of the core mold surface is of great significance for improving the quality and performance of electroplated metal grid lines.

[0032] In order to solve the above technical problems, the present disclosure provides a method for electrodeposition of metal gate lines for preparing metal gate lines based on a reversibly controllable wettability core mold. Figure 1 As shown in , it mainly includes the following steps:

[0033] In step S110, a mixture of polydimethylsiloxane prepolymer and curing agent is poured on the original template with the grid line pattern, and solidified after removing all bubbles, and demolded after cooling to room temperature to obtain a polydimethylsiloxane core mold with a grid line structure;

[0034] In step S120, the polydimethylsiloxane core mold is placed in a chemical metal plating solution and stirred to react at room temperature to deposit a metal conductive layer on the surface of the polydimethylsiloxane core mold;

[0035] In step S130, the polydimethylsiloxane core mold with a metal conductive layer deposited on the surface is irradiated with ultraviolet light to change the wettability of the surface of the polydimethylsiloxane core mold from hydrophobic to superhydrophilic;

[0036] In step S140, the super-hydrophilic polydimethylsiloxane core mold is bonded to the silicon substrate and immersed in an electroplating solution as a cathode for electrodeposition to obtain a metal gate line structure;

[0037] In step S150, the polydimethylsiloxane core mold after electrodeposition is subjected to low-temperature heat treatment to achieve super-hydrophobic conversion of the wettability of the surface of the polydimethylsiloxane core mold;

[0038] In step S160 , the metal gate line structure is removed from the super-hydrophobic polydimethylsiloxane core mold to obtain the metal gate line.

[0039] Next, the method for electro-deposition of the metal gate line in the embodiment of the present disclosure is described in detail.

[0040] In step S110, a mixture of polydimethylsiloxane prepolymer and curing agent is post-cast on the original template with the grid line pattern, solidified and formed after removing all bubbles, and demolded after cooling to room temperature to obtain a polydimethylsiloxane core mold with a grid line structure.

[0041] In the disclosed embodiment, a soft etching forming process of a core mold with a gate line structure is first performed. Polydimethylsiloxane prepolymer (PDMS) corresponds to a curing agent, and the mixing ratio of the polydimethylsiloxane prepolymer and the curing agent is 10:1. The original template has a gate line pattern. After the polydimethylsiloxane prepolymer and the curing agent are evenly mixed in a ratio of 10:1, the mixture can be poured on the original template with the gate line pattern. Furthermore, curing and forming can be performed after removing all bubbles, and demolding can be performed after cooling to room temperature to obtain a polydimethylsiloxane core mold with a gate line structure. Among them, the gate line structure can be determined according to the gate line pattern in the original template.

[0042] The air bubbles can be removed in a vacuum drying dish and then put into an oven for curing. The curing temperature can be 100° C. After curing, the mold can be cooled and demolded after cooling to room temperature to obtain a PDMS core mold with a grid line structure.

[0043] In some embodiments, the PDMS prepolymer may be 50 mL, and the curing agent may be 5 mL. The curing temperature may be 100° C., and the curing time may be 30 minutes. Of course, the curing temperature and time may be adjusted according to actual needs.

[0044] In step S120, the polydimethylsiloxane core mold is placed in a chemical metal plating solution and stirred for reaction at room temperature to deposit a metal conductive layer on the surface of the polydimethylsiloxane core mold.

[0045] In the disclosed embodiment, the surface of the polydimethylsiloxane core mold may be subjected to a conductive treatment. The chemical metal plating solution may be a silver chemical plating solution, a nickel chemical plating solution, or a copper chemical plating solution. The temperature of the stirring reaction may be room temperature, and the stirring time of the stirring reaction may be 10 to 60 minutes, which may be determined according to actual conditions.

[0046] The polydimethylsiloxane core mold is placed in a chemical metal plating solution and stirred at room temperature to react, and a metal conductive layer corresponding to the chemical metal plating solution can be deposited on the surface of the polydimethylsiloxane core mold. For example, a nano silver layer, a nano nickel layer, or a nano copper layer can be deposited on the surface of the polydimethylsiloxane core mold. The thickness of the metal conductive layer can be determined according to actual needs, as long as it can conduct electricity.

[0047] When the chemical metal plating solution is a silver chemical plating solution, the preparation method of the silver chemical plating solution comprises: adding 0.3 g of silver nitrate into 30 mL of deionized water, and after the silver nitrate is completely dissolved in the water, slowly dripping ammonia water until the solution changes from clear to turbid, and then stopping the dripping when the turbid changes to colorless and transparent to obtain a silver ammonia solution; dripping 0.3 g of glucose into 30 mL of deionized water to obtain a glucose solution; and stirring and mixing the silver ammonia solution and the glucose solution at room temperature for 30 minutes to prepare a silver chemical plating solution.

[0048] When the chemical plating metal solution is a nickel chemical plating solution, the nickel chemical plating solution may include the following components: nickel chloride (40 g / L), sodium hypophosphite (10 g / L), sodium acetate (4 g / L), sodium citrate (10 g / L), and the pH value of the nickel chemical plating solution may be adjusted to 5.0 by dilute hydrochloric acid.

[0049] When the chemical metal plating solution is a copper chemical plating solution, the copper chemical plating solution may include the following components: copper sulfate (15 g / L), potassium sodium tartrate (20 g / L), sodium hydroxide (10 g / L), and sodium borohydride (1.5 g / L). The pH value of the copper chemical plating solution can be adjusted to 13.0 by dilute hydrochloric acid.

[0050] By placing the polydimethylsiloxane core mold in a chemical metal plating solution and stirring the reaction at room temperature for 10 to 60 minutes, a metal conductive layer is deposited on the surface of the polydimethylsiloxane core mold, and the surface of the polydimethylsiloxane core mold can be conductively treated.

[0051] In step S130, the polydimethylsiloxane core mold with a metal conductive layer deposited on the surface is irradiated with ultraviolet light to change the wettability of the surface of the polydimethylsiloxane core mold from hydrophobic to superhydrophilic.

[0052] In the embodiment of the present disclosure, the super-hydrophilic modification of the surface wettability of the polydimethylsiloxane core mold can be performed. For example, the polydimethylsiloxane core mold with a metal conductive layer deposited on the surface can be placed under ultraviolet light for ultraviolet light irradiation, so that the wettability of the surface of the polydimethylsiloxane core mold changes from hydrophobic to super-hydrophilic, thereby obtaining a polydimethylsiloxane core mold with a super-hydrophilic surface. The ultraviolet light irradiation time is 2 to 30 hours, for example, it can be 2 hours, 18 hours or 30 hours.

[0053] In step S140, the super-hydrophilic polydimethylsiloxane core mold is bonded to the silicon substrate and immersed in an electroplating solution as a cathode for electrodeposition to obtain a metal gate line structure.

[0054] In the embodiments of the present disclosure, electroplating forming of the metal grid line structure can be performed. Exemplarily, the silicon substrate can be a silicon substrate after conductive treatment. The bonding process can be achieved by a clamp. The super-hydrophilic polydimethylsiloxane core mold after ultraviolet light irradiation and the silicon substrate after conductive treatment can be tightly bonded with a clamp, and then immersed in a plating solution as a cathode for electrodeposition, thereby obtaining a metal grid line structure. The plating solution can be a copper plating solution, a nickel plating solution, or a copper-nickel alloy plating solution. The electrodeposition can be a direct current electrodeposition or a pulse electrodeposition, and the current density of the electrodeposition is 1~10A / dm 2 For example, the current density can be 3A / dm 2 , 1A / dm² or 10A / dm². The current density of the electrodeposition can be determined according to the influencing factors, which may include at least one or more of the type of electroplating solution, the method of electrodeposition, the size of the pattern and the thickness.

[0055] When the electroplating solution is a copper electroplating solution, the electroplating solution contains the following components: copper sulfate (100 g / L), sulfuric acid (150 g / L), sodium chloride (1 g / L), gelatin (5 mg / L), and polyethylene glycol (5 mg / L).

[0056] When the electroplating solution is a nickel electroplating solution, the nickel electroplating solution contains the following components: nickel sulfate (280 g / L), boric acid (40 g / L), nickel chloride (55 g / L), saccharin (10 g / L) and sodium dodecyl sulfate (2 g / L).

[0057] When the electroplating solution is a copper-nickel alloy electroplating solution, the electroplating solution contains the following components: copper sulfate (300 g / L), nickel sulfate (80 g / L), sodium chloride (50 g / L), boric acid (30 g / L), saccharin (10 g / L) and sodium dodecyl sulfate (1 g / L).

[0058] When the metal grid structure is deposited to a target thickness, the super-hydrophilic polydimethylsiloxane core mold can be taken out and immersed in deionized water for ultrasonic cleaning. The target thickness can be determined according to actual needs, for example, it can be 20-100 μm, etc.

[0059] In step S150, the polydimethylsiloxane core mold after electrodeposition is subjected to low-temperature heat treatment to achieve super-hydrophobic conversion of the wettability of the surface of the polydimethylsiloxane core mold.

[0060] In the disclosed embodiment, super-hydrophobic modification of the wettability of the surface of the polydimethylsiloxane core mold can be performed. For example, the polydimethylsiloxane core mold after electrodeposition can be subjected to low-temperature heat treatment in an oven, and the temperature of the low-temperature heat treatment can be 100-150°C, and the time of the low-temperature heat treatment can be 5-60 minutes. The temperature of the low-temperature heat treatment is different, and the time of the low-temperature heat treatment is also different, and the temperature can be negatively correlated with the time.

[0061] In some embodiments, when the electroplating solution is a copper electroplating solution, the low-temperature heat treatment may be heat treatment in an oven at 120°C for 30 minutes; when the electroplating solution is a nickel electroplating solution, the low-temperature heat treatment may be heat treatment in an oven at 100°C for 60 minutes; when the electroplating solution is a copper-nickel alloy electroplating solution, the low-temperature heat treatment may be heat treatment in an oven at 150°C for 5 minutes.

[0062] In the disclosed embodiment, by performing low temperature heat treatment on the deposited polydimethylsiloxane core mold, the surface of the polydimethylsiloxane core mold can re-adsorb carbon pollutants in the air, thereby achieving super-hydrophobic conversion of the wettability of the surface of the polydimethylsiloxane core mold and increasing the water contact angle of the surface of the polydimethylsiloxane core mold. The interfacial adhesion between the polydimethylsiloxane core mold and the electroplated gate line can be reduced through the super-hydrophobic conversion of the wettability of the surface of the polydimethylsiloxane core mold.

[0063] In step S160 , the metal gate line structure is removed from the super-hydrophobic polydimethylsiloxane core mold to obtain the metal gate line.

[0064] In the disclosed embodiment, the demolding and post-processing of the metal grid line structure can be performed. After cooling to room temperature, the metal grid line structure can be removed from the super-hydrophobic polydimethylsiloxane core mold by manual demolding, and then ultrasonically cleaned to obtain the desired sample, which is the prepared metal grid line. Among them, the polydimethylsiloxane core mold has excellent elasticity and flexibility, and the polydimethylsiloxane core mold after demolding can be reused.

[0065] On this basis, the metal gate line electrodeposition method disclosed in the present invention can be specifically described in combination with the embodiments.

[0066] In some embodiments, the metal grid lines can be prepared by electroplating metal micro-parts without hydrophilic or hydrophobic modification, which specifically includes the following steps:

[0067] Step 1: Soft etching of PDMS core mold: Pour a PDMS mixture consisting of 50 mL PDMS prepolymer and 5 mL curing agent on the surface of the original template, then remove all bubbles in a vacuum drying dish, put it in an oven at 100°C for curing for 30 minutes, and demold it after cooling to room temperature to obtain a PDMS core mold with a grid line structure.

[0068] Step 2: Place the PDMS core mold in step 1 into a silver chemical plating solution and stir for 10 minutes at room temperature to deposit a nanosilver layer on the surface of the PDMS core mold, thereby achieving conductive treatment.

[0069] Step 3: Electroplating of metal grid line structure: Immerse the PDMS core mold with surface conductivity treatment into copper electroplating solution, and prepare the copper grid line structure by direct current electrodeposition. The current density of electrodeposition is 3A / dm².

[0070] Step 4: Demolding and post-processing of the metal grid structure: After the core mold microcavity is fully cast, the copper grid structure is removed by manual demoulding, and then ultrasonic cleaning is performed to obtain the desired sample.

[0071] Figure 2 The morphology of the copper grid line structure with a line width of 20~70μm prepared without hydrophilic / hydrophobic modification. Figure 2 It can be seen that the prepared copper grid line structure has obvious "lost casting" defects, making it difficult to achieve microstructure replication. In addition, during the demolding process, due to the strong interface adhesion between the PDMS core mold and the copper grid line, the PDMS core mold microstructure breaks and remains in the grid line structure cavity, making the PDMS core mold unable to be reused.

[0072] In order to solve the technical problems existing in the related art, the present disclosure provides a method for electrodeposition of metal grid lines based on a wettability reversible control mandrel, which is mainly used to prepare a grid line structure in a solar cell. The following is a detailed description of the method for electrodeposition of metal grid lines in conjunction with the embodiments.

[0073] It should be noted that, during the entire metal grid line preparation process, parameters such as the stirring time of the PDMS core mold in the chemical metal plating solution, the ultraviolet light irradiation time, the low temperature heat treatment temperature, and the low temperature heat treatment time can be adjusted. In addition, the composition of the chemical metal plating solution and the electroplating solution can also be adjusted.

[0074] Example 1

[0075] The electroplating method of metal grid lines based on silver chemical plating solution mainly includes the following steps:

[0076] Step 1, PDMS core mold soft etching forming: pour PDMS mixture 2 consisting of 50 mL PDMS prepolymer and 5 mL curing agent on the surface of the original template 1 with the grid line pattern, then remove all bubbles in a vacuum drying dish, put it in an oven at 100°C for 30 minutes, and demold it after cooling to room temperature to obtain a PDMS core mold 3 with a grid line structure. The specific process of PDMS core mold soft etching forming can be as follows Figure 3 shown.

[0077] Step 2: Conductive treatment of the surface of the PDMS core mold: Place the PDMS core mold 3 with the grid line structure in step 1 into a silver chemical plating solution and stir for 10 minutes at room temperature to deposit the nanosilver layer 4 on the surface of the PDMS core mold, thereby achieving conductive treatment. Figure 4 shown.

[0078] The preparation process of the silver chemical plating solution is as follows: first, add 0.3 g of silver nitrate to 30 mL of deionized water, wait for it to be completely dissolved in water, slowly add ammonia water until the solution changes from clear to turbid, and then stop adding when it changes from turbid to colorless and transparent to obtain a silver ammonia solution; secondly, drop 0.3 g of glucose into 30 mL of deionized water to obtain a glucose solution; finally, stir and mix the silver ammonia solution and the glucose solution at room temperature for 30 min to prepare a silver chemical plating solution.

[0079] Step 3: Super-hydrophilic modification of the wettability of the core mold surface: The PDMS core mold 3 with the chemically silver-plated surface in step 2 is placed under ultraviolet light for 18 hours to obtain a super-hydrophilic PDMS core mold 5. Figure 5 Figure (a) and Figure 5 As shown in Figure (b), after UV irradiation, the water contact angle on the surface of the PDMS core mold changes from 83° to 4°.

[0080] Step 4: Electroplating of metal grid line structure: The ultra-hydrophilic PDMS core mold 5 after UV irradiation is tightly fitted with the conductive silicon substrate 6 with a clamp, and then immersed in the copper electroplating solution as a cathode for DC electroplating. The current density during the DC electroplating process is 3A / dm². When the copper ions 7 are deposited in the core mold cavity to reach the required target thickness, the metal grid line structure 8 is formed. After the metal grid line structure 8 is formed, the PDMS core mold after electroplating is taken out and immersed in deionized water for ultrasonic cleaning. The specific process can be as follows: Figure 6 shown.

[0081] The copper electroplating solution contains the following components: copper sulfate (100 g / L), sulfuric acid (150 g / L), sodium chloride (1 g / L), gelatin (5 mg / L), and polyethylene glycol (5 mg / L).

[0082] Step 5: Super-hydrophobic modification of the wettability of the PDMS core mold surface: The PDMS core mold deposited in step 4 is placed in an oven for heat treatment at 120°C for 30 min, so that the surface of the PDMS core mold re-adsorbs carbon pollutants in the air.

[0083] refer to Figure 5 Figure (b) and Figure 5As shown in Figure (c), after low-temperature heat treatment in an oven, the water contact angle of the PDMS core mold surface changes from 4° to 151°. The superhydrophobic conversion of the wettability of the PDMS core mold surface can reduce the interfacial adhesion between the core mold and the electroplated grid line.

[0084] Step 6: Demolding and post-processing of the metal grid structure: After cooling to room temperature, the metal grid structure 9 is removed by manual demoulding, and then ultrasonically cleaned to obtain the desired sample. The PDMS core mold has excellent elasticity and flexibility, so the core mold can be reused after demoulding.

[0085] Figure 7 The morphology of the copper grid line structure with a line width of 20 μm prepared according to Example 1 is shown in FIG. Figure 7 It can be seen that the copper grid line structure formed by electroplating in the embodiment of the present disclosure is complete and has no defects. It can be considered that this method has excellent replication forming accuracy.

[0086] Example 2

[0087] The electroplating method of metal grid lines based on nickel chemical plating solution mainly includes the following steps:

[0088] Step 1, PDMS core mold soft etching forming: pour PDMS mixture 2 consisting of 50mL PDMS prepolymer and 5mL curing agent on the surface of the original template 1, then remove all bubbles in a vacuum drying dish, put it in an oven at 100°C for curing for 30 minutes, and demold it after cooling to room temperature to obtain a PDMS core mold 3 with a grid line structure. The specific process of PDMS core mold soft etching forming can be as follows Figure 3 shown.

[0089] Step 2: Conductive treatment of the surface of the PDMS core mold: Place the PDMS core mold in a nickel chemical plating solution and stir it for 60 minutes at room temperature to deposit a nano-nickel layer on the surface of the PDMS core mold, thereby achieving conductive treatment.

[0090] The nickel chemical plating solution contains one or more of the following components: nickel chloride (40 g / L), sodium hypophosphite (10 g / L), sodium acetate (4 g / L), and sodium citrate (10 g / L). In addition, the pH value of the nickel chemical plating solution can be adjusted to 5.0 by dilute hydrochloric acid.

[0091] Step 3: Super-hydrophilic modification of the surface wettability of the PDMS core mold: The PDMS core mold with the chemically nickel-plated surface in step 2 is placed under ultraviolet light for 30 hours to change the surface wettability of the PDMS core mold from hydrophobic to super-hydrophilic. Figure 5 Figure (a) and Figure 5 As shown in Figure (b), after UV irradiation, the water contact angle on the surface of the PDMS core mold can be changed from 83° to 4°.

[0092] Step 4: Electroplating of metal grid line structure: The nickel grid line structure is prepared by pulse electrodeposition in a nickel electroplating solution, and the current density during the pulse electrodeposition process is 1A / dm².

[0093] refer to Figure 6 As shown in , the specific operation steps of electroplating the metal grid line structure include: tightly fitting the PDMS core mold 5 with a super-hydrophilic surface after ultraviolet light irradiation and the silicon substrate 6 after conductive treatment with a clamp, and then immersing them together in a nickel electroplating solution as a cathode for pulse electrodeposition. The current density during the pulse electrodeposition process is 1A / dm². When the nickel ions 7 are deposited in the core mold cavity to reach the required target thickness, the metal grid line structure 8 is formed. After the metal grid line structure 8 is formed, the PDMS core mold after electrodeposition is taken out and immersed in deionized water for ultrasonic cleaning.

[0094] The nickel plating solution contains the following components: nickel sulfate (280 g / L), boric acid (40 g / L), nickel chloride (55 g / L), saccharin (10 g / L) and sodium dodecyl sulfate (2 g / L).

[0095] Step 5: Super-hydrophobic modification of the wettability of the PDMS core mold surface: The PDMS core mold deposited in step 4 is placed in an oven for heat treatment at 100°C for 60 min, so that the surface of the PDMS core mold re-adsorbs carbon pollutants in the air, thereby achieving super-hydrophobic conversion of the wettability of the PDMS core mold surface.

[0096] refer to Figure 5 Figure (b) and Figure 5 As shown in Figure (c), after low-temperature heat treatment in an oven, the water contact angle of the PDMS core mold surface changes from 4° to 151°. The superhydrophobic conversion of the wettability of the PDMS core mold surface can reduce the interfacial adhesion between the core mold and the electroplated grid line.

[0097] Step 6: Demolding and post-processing of the metal grid structure: After cooling to room temperature, the nickel grid structure is removed by manual demoulding, and then ultrasonic cleaning is performed to obtain the desired sample. The PDMS core mold has excellent elasticity and flexibility, so the core mold can be reused after demoulding.

[0098] Figure 8 The morphology of the nickel gate line structure with a line width of 15 μm prepared according to Example 2 is shown in FIG. Figure 8 It can be seen that the nickel gate line structure prepared according to Example 2 is continuous and complete, so the method in step S110 to step S160 can shorten the process of preparing the gate line structure, reduce costs, and improve accuracy.

[0099] Example 3

[0100] The electroplating method of the metal grid line based on the copper chemical plating solution mainly includes the following steps:

[0101] Step 1, PDMS core mold soft etching forming: pour PDMS mixture 2 consisting of 50mL PDMS prepolymer and 5mL curing agent on the surface of the original template 1, then remove all bubbles in a vacuum drying dish, put it in an oven at 100°C for curing for 30 minutes, and demold it after cooling to room temperature to obtain a PDMS core mold 3 with a grid line structure. The specific process of PDMS core mold soft etching forming can be as follows Figure 3 shown.

[0102] Step 2: Conductive treatment of the surface of the PDMS core mold: Place the PDMS core mold in a copper chemical plating solution and stir it for 30 minutes at room temperature to deposit a nano-copper layer on the surface of the PDMS core mold, thereby achieving conductive treatment.

[0103] The copper chemical plating solution contains one or more of the following components: copper sulfate (15 g / L), potassium sodium tartrate (20 g / L), sodium hydroxide (10 g / L), sodium borohydride (1.5 g / L), and the pH value of the copper chemical plating solution can be adjusted to 13.0 by dilute hydrochloric acid.

[0104] Step 3: Super-hydrophilic modification of the wettability of the core mold surface: The PDMS core mold with the surface chemical copper plating layer in step 2 is placed under ultraviolet light for 2 hours to change the wettability of the core mold surface from hydrophobic to super-hydrophilic.

[0105] Step 4: Electroplating of metal grid line structure: Pulse electrodeposition is used to prepare the metal grid line structure in a copper-nickel alloy electroplating solution, and the current density of the pulse electrodeposition is 10A / dm².

[0106] refer to Figure 6 As shown in , the specific operation steps of electroplating the metal grid line structure include: tightly fitting the PDMS core mold 5 whose surface is super hydrophilic after ultraviolet light irradiation and the silicon substrate 6 after conductive treatment with a clamp, and then immersing them together in a copper-nickel alloy electroplating solution as a cathode for pulse electrodeposition. The current density during the pulse electrodeposition process is 10A / dm². When the metal ions 7 such as copper ions and nickel ions are deposited in the core model cavity to reach the required target thickness, a metal grid line structure 8 is formed. After the metal grid line structure 8 is formed, the PDMS core mold after electrodeposition is taken out and immersed in deionized water for ultrasonic cleaning. Among them, the anode is composed of a copper sheet and a nickel sheet, and the area ratio of the copper sheet to the nickel sheet is 4:1.

[0107] The copper-nickel alloy electroplating solution contains one or more of the following components: copper sulfate (300 g / L), nickel sulfate (80 g / L), sodium chloride (50 g / L), boric acid (30 g / L), saccharin (10 g / L) and sodium dodecyl sulfate (1 g / L).

[0108] Step 5: Super-hydrophobic modification of the wettability of the PDMS core mold surface: The PDMS core mold deposited in step 4 is placed in an oven for heat treatment at 150°C for 5 minutes, so that the surface of the PDMS core mold re-adsorbs carbon pollutants in the air, achieving super-hydrophobic conversion of the wettability of the PDMS core mold surface.

[0109] Step 6: Demolding and post-processing of the metal grid structure: After cooling to room temperature, the copper-nickel alloy grid structure is removed by manual demoulding, and then ultrasonic cleaning is performed to obtain the desired sample. The PDMS core mold can be reused after demoulding due to its excellent elasticity and flexibility.

[0110] Fig. 9 The morphology of the copper-nickel alloy gate line structure with a line width of 30 μm prepared according to Example 3 is shown in FIG. Fig. 9 It can be seen that the copper-nickel alloy grid line structure prepared in the embodiment of the present disclosure is complete and accurately replicates the original template microstructure. Therefore, the technical solution in the embodiment of the present disclosure has excellent replication forming accuracy.

[0111] In summary, in the embodiments of the present disclosure, the wettability of the surface of the polydimethylsiloxane core mold can be changed from hydrophobic to super-hydrophilic through ultraviolet light irradiation, and the wettability of the surface of the polydimethylsiloxane core mold can be converted to super-hydrophobic through low-temperature heat treatment, so as to improve the liquid phase mass transfer efficiency during the electroplating process and reduce the interfacial adhesion during the demolding process. The process of regulating the hydrophobicity of the core mold surface is simplified, the cost is reduced and the stability is improved. Since the required sample can be prepared without post-treatment and degumming, the process of preparing metal grid lines is shortened and the preparation efficiency is improved. The metal grid lines are prepared by replacing the existing graphic process with the polydimethylsiloxane core mold, which reduces the preparation cost of the metal grid lines. By depositing a nanoscale metal conductive layer with reversible wettability on the surface of the polydimethylsiloxane core mold, the electroplating core mold is endowed with excellent conductivity, the current density in the microcavity is increased, the deposition efficiency and forming quality of the metal grid lines are improved, and the accuracy of the metal grid lines is improved.

[0112] In an embodiment of the present disclosure, a metal gate line is further provided. The metal gate line can be prepared according to the method of step S110 to step S160.

[0113] In the disclosed embodiment, a PDMS core mold with a grid line structure is prepared by soft etching technology, and its surface is conductively treated by chemically plating a metal layer; the PDMS core mold with a chemically plated metal layer is placed under ultraviolet light to irradiate, so that the wettability of the core mold surface changes from hydrophobic to super-hydrophilic; the super-hydrophilic PDMS core mold is immersed in a plating solution for electrodeposition to prepare a grid line structure; after the grid line is deposited to the required thickness, the core mold is placed in an oven for low-temperature heat treatment, so that the surface of the core mold re-adsorbs carbon pollutants in the air, thereby achieving a super-hydrophobic conversion of the wettability of the core mold surface; the grid line structure is removed from the core mold by manual demolding. In the disclosed embodiment, the surface wettability of the core mold is modified to be super-hydrophilic and super-hydrophobic by ultraviolet light irradiation and low-temperature heat treatment, respectively, to overcome the problems of low efficiency of metal grid line electrodeposition and difficulty in post-treatment glue removal, simplify the process of regulating the hydrophobicity of the core mold surface, reduce costs and improve stability, and achieve short-process, low-cost and high-precision preparation and forming of metal grid line structures.

[0114] In this exemplary embodiment, a solar cell is further provided, wherein the solar cell has metal grid lines prepared by the above steps S110 to S160, which are not particularly limited in this exemplary embodiment.

[0115] In addition, the above-mentioned figures are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present disclosure, and are not intended to be limiting. It is easy to understand that the processes shown in the above-mentioned figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.

[0116] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

[0117] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A method for electrodeposition of a metal grid line, characterized in that: include: A mixture of polydimethylsiloxane prepolymer and curing agent is poured on an original template with a grid line pattern, solidified and formed after all bubbles are removed, and demolded after cooling to room temperature to obtain a polydimethylsiloxane core mold with a grid line structure; placing the polydimethylsiloxane core mold in a chemical metal plating solution and stirring the solution at room temperature to deposit a metal conductive layer on the surface of the polydimethylsiloxane core mold; The polydimethylsiloxane core mold with a metal conductive layer deposited on the surface is irradiated with ultraviolet light to change the wettability of the surface of the polydimethylsiloxane core mold from hydrophobic to superhydrophilic; The super-hydrophilic polydimethylsiloxane core mold is bonded to the silicon substrate and immersed in the electroplating solution as a cathode for electrodeposition to form a metal grid line structure; The polydimethylsiloxane core mold after electrodeposition is subjected to low-temperature heat treatment to achieve super-hydrophobic conversion of the surface wettability of the polydimethylsiloxane core mold; the temperature of the low-temperature heat treatment is 100-150° C.; The metal grid line structure is taken out from the super-hydrophobic polydimethylsiloxane core mold to obtain the metal grid line.

2. The method for electrodeposition of metal grid lines according to claim 1, characterized in that: The metal conductive layer is any one of silver, nickel and copper.

3. The method for electrodeposition of metal grid lines according to claim 1, characterized in that: The ultraviolet light irradiation time is 2 to 30 hours.

4. The method for electrodeposition of metal grid lines according to claim 1, characterized in that: The electrodeposition includes direct current electrodeposition or pulse electrodeposition, and the current density of the electrodeposition is 1-10 A / dm 2 .

5. The method for electrodeposition of metal grid lines according to claim 1, characterized in that: The low temperature heat treatment time is 5 to 60 minutes.

6. The method for electrodeposition of metal grid lines according to claim 1, characterized in that: The mixing ratio of the polydimethylsiloxane prepolymer and the curing agent is 10:

1.

7. The method for electrodeposition of metal grid lines according to claim 1, characterized in that: The curing temperature is 100°C.

8. The method for electrodeposition of metal grid lines according to claim 1, characterized in that: The super-hydrophilic polydimethylsiloxane core mold is bonded to the silicon substrate and immersed in the electroplating solution as a cathode for electrodeposition, including: The super-hydrophilic polydimethylsiloxane core mold is attached to the conductive silicon substrate through a fixture and immersed in the electroplating solution as a cathode for electrodeposition; Wherein, the electroplating solution includes one of a copper electroplating solution, a nickel electroplating solution and a copper-nickel alloy electroplating solution.

9. The method for electrodeposition of metal grid lines according to claim 8, characterized in that: The method further comprises: When the metal grid line structure is deposited to a target thickness, the super-hydrophilic polydimethylsiloxane core mold is taken out and immersed in deionized water for ultrasonic cleaning.

10. A metal grid line, characterized in that: The metal grid line is prepared by the metal grid line electrodeposition method according to any one of claims 1-9.

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