Preparation method of wet etching copper grid line
The copper gate wire was prepared on the BC cell by wet etching, which solved the problem of poor attachment of the metal gate wire to the cell, and improved the conductivity and photoelectric conversion efficiency of the cell.
Patent Information
- Application Number
- CN202510021458.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-03
- Publication Date
- 2025-04-22
AI Technical Summary
The poor attachment between the metal gate lines of existing BC batteries and the cell is caused by low conductivity and affecting the photoelectric conversion efficiency of the cell.
The copper gate wire was prepared by wet etching method. By depositing a transparent conductive film and a bottom seed layer on the cell, a mask layer was prepared in the non-P/N electrode area using the mask layer covering process, and metal plating and deposition were performed in the P/N electrode area, and finally the mask layer, the bottom seed layer and the transparent conductive film were removed to obtain the copper gate wire structure.
The bonding force between the metal gate line and the cell is improved, the isolation effect between the P/N electrode areas is enhanced, and the conductivity and photoelectric conversion efficiency of the cell are improved.
Smart Images
Figure CN119866095A_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the technical field of solar cell manufacturing, and in particular to a method for preparing a wet-etched copper grid line. Background Art
[0002] BC (Back Contact) cells are a type of photovoltaic cell with a non-shading front design. They have the characteristics of high conversion efficiency and can be stacked and connected in series with other different types of photovoltaic cells. They are considered to be one of the important development directions of the future photovoltaic industry.
[0003] However, the metallization on the back of BC cells in the past used the traditional printing silver paste method to prepare the P / N electrode grid lines with silver paste. However, due to the high silver price, the cost of the battery cell remains high, and the high resistivity of the silver paste cannot improve the conversion efficiency of the battery cell.
[0004] In addition, on the P / N electrode grid line area, it is necessary to prepare a nickel layer by chemical deposition, and form a nickel-silicon alloy layer by annealing process to obtain a good ohmic contact as the seed layer of the electroplating process. However, these process flows are complicated, lengthy and difficult to accurately control the required process results. For example, the thickness of nickel deposition, the thickness of nickel silicon formation, etc., will affect the final BC battery production yield and the final battery photoelectric conversion efficiency, making BC batteries unable to be mass-produced and popularized. Summary of the invention
[0005] The present application provides a method for preparing a copper grid line by wet etching, which solves the technical problem that the existing preparation method easily leads to poor adhesion between the metal grid line and the battery cell, resulting in low conductivity of the grid line.
[0006] In order to solve at least one of the above technical problems, the technical solution adopted in this application is:
[0007] A method for preparing a wet-etched copper grid line, comprising the following steps:
[0008] Obtaining a battery cell having a P / N junction electrode region;
[0009] Depositing a transparent conductive film on the cell;
[0010] depositing a bottom seed layer on the transparent conductive film;
[0011] Applying a mask layer to the non-P / N junction electrode area;
[0012] Depositing metal gate lines in the P / N junction electrode region;
[0013] sequentially removing the mask layer, etching back the bottom seed layer, and etching the transparent conductive film;
[0014] A BC cell with a copper grid structure is obtained.
[0015] Furthermore, the battery cell having the P / N junction electrode region is provided with the P / N junction electrode region on the back side of the battery cell.
[0016] Furthermore, when preparing the transparent conductive film, a vacuum deposition process is used to deposit a layer of transparent conductive film on the back side of the cell having the P / N junction electrode region, and the thickness of the film is in the range of 10-200 nm.
[0017] Furthermore, the transparent conductive film material is:
[0018] Indium tin oxide film, wherein the mass ratio of In2O3 to SnO2 is in the range of 97:3-99:1; or,
[0019] Indium tungsten oxide film, wherein the mass ratio of In2O3 to W is in the range of 90:10-99.7:0.3; or,
[0020] Zinc oxide aluminum film, wherein the mass ratio of ZnO to Al2O3 ranges from 90:10 to 99:1.
[0021] Furthermore, the bottom seed layer is deposited on the transparent conductive film by using a vacuum deposition process to deposit the bottom seed layer on the prepared transparent conductive film cell, wherein the bottom seed layer material can be a single metal layer or a metal alloy layer, and the thickness range after preparation is 10-200nm.
[0022] Furthermore, a printing coating process, a spray coating process, a spin coating process or an imprinting process is used to prepare a mask layer on the bottom seed layer, and the mask layer is transferred to the non-P / N junction electrode area; and then it is cured; wherein,
[0023] During curing, the curing temperature is 60-200° C., the time is 60-600s, and the thickness of the cured mask layer is 3-50um.
[0024] Furthermore, the metal gate line is deposited in the P / N junction electrode region, specifically: controlling the cell to have a current density of 5-50A / m 2 In the electroplating space area, electroplating is continued for 300-900s to form electroplated metal grid lines on the exposed bottom seed layer; the width of the obtained metal grid lines is 30-500um and the thickness is 2-5um.
[0025] Furthermore, when removing the mask layer on the non-P / N junction electrode area, the cell is transferred to the removal tank section, the temperature of the removal solution is adapted to be 35-55°C, the concentration range of the spray solution is 1.5-7%, and the spray pressure range of the solution is controlled to be 0.5-3.5kg / cm 2 , spraying time is 30-300s.
[0026] Furthermore, when etching back the bottom seed layer, the cell is transferred to a removal solution tank section to remove the bottom seed layer on the non-P / N junction electrode region, wherein the removal solution is an inorganic acid with a concentration range of 1-2%; including one or more of sulfuric acid, hydrochloric acid, boric acid, phosphoric acid, and nitric acid;
[0027] The temperature of the removal solution is 20-35°C and the spray pressure range is 0.5-2.5 kg / cm 2 , and the spraying time is 30-300s.
[0028] Furthermore, the transparent conductive film on the non-P / N junction electrode area is etched, and based on the position of the P / N junction electrode area, the etching paste is applied to the non-P / N junction electrode area on the battery cell, and the etching temperature is set to 130-180°C, and the etching time is 30-300s; the battery cell is then rinsed with pure water or an aqueous solution containing sodium hydroxide or potassium hydroxide with a concentration of 0.3-2%, and a BC battery with a copper grid structure prepared by wet etching can be obtained.
[0029] A method for preparing a wet-etched copper grid line designed in this application is adopted, and the conventional silicon nitride passivation layer is replaced by a transparent conductive layer and a bottom seed layer; the non-P / N electrode area is prepared by a mature, convenient and highly controllable yellow light patterning process (mask layer covering); the P / N electrode area is then subjected to a metal electroplating deposition process, and after the overall metallization is completed, the mask layer, bottom metal layer and transparent conductive layer on the non-P / N electrode area are removed in sequence; finally, a metal copper fine grid line with a simple process, air operation and complete isolation by wet etching is obtained, thereby improving the isolation effect between the P / N electrode areas. This method not only solves the technical problem of poor adhesion between the metal grid line and the cell, but also improves the bifaciality of the cell module and the grid line conductivity of the P / N electrode through the production of fine-line patterned metal grid lines, thereby ultimately improving the photoelectric conversion efficiency of the BC cell. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 It is a flow chart of a method for preparing a wet-etched copper grid line in the present application;
[0031] Figure 2 It is a schematic diagram of the structure of a battery cell with a P / N junction electrode region in the present application;
[0032] Figure 3 It is a schematic structural diagram of a battery cell with a transparent conductive film in the present application;
[0033] Figure 4 is a schematic diagram of the structure of a battery cell with a bottom seed layer in the present application;
[0034] Figure 5is a schematic structural diagram of a cell with a mask layer in the present application;
[0035] Figure 6 is a schematic diagram of the structure of a battery cell with metal grid lines in this application;
[0036] Figure 7 is a schematic diagram of the structure of a battery cell after removing the mask layer in this application;
[0037] Figure 8 It is a structural schematic diagram of the wet etching transmission mechanism in the present application;
[0038] Fig. 9 is a schematic diagram of the structure of a battery cell after removing the bottom seed layer in this application;
[0039] Fig.10 It is a schematic diagram of the structure of the battery cell after etching the transparent conductive film in this application.
[0040] In the figure:
[0041] 10. Cell 20. Non-P / N junction electrode region 30. Transparent conductive film
[0042] 40, bottom seed layer 50, mask layer 60, metal gate line
[0043] 70. Spray nozzle DETAILED DESCRIPTION
[0044] The present application is described in detail below with reference to the accompanying drawings and specific embodiments.
[0045] This embodiment provides a method for preparing a wet-etched copper grid line. Figure 1 As shown, the steps include:
[0046] S1. Obtain a battery cell having a P / N junction electrode region.
[0047] like Figure 2 As shown, on the back of the cell 10, the P / N junction electrode area is prepared in advance, and is evenly spaced and distributed on the back of the cell 10, and the front drawing is omitted. Among them, the area between the P junction and the N junction is the non-P / N junction electrode area 20.
[0048] S2. Depositing a transparent conductive film on the battery cell.
[0049] like Figure 3 As shown, a transparent conductive film 30 is prepared by a vacuum deposition process, that is, a layer of transparent conductive film 30 is deposited on the back of the battery cell 10 having a P / N junction electrode area. The transparent conductive film 30 not only covers the P / N junction electrode area but also covers the non-P / N junction electrode area 20, and the thickness of the formed transparent conductive film 30 ranges from 10 to 200 nm.
[0050] In this embodiment, the material of the transparent conductive film 30 may be an indium tin oxide film, an indium tungsten oxide film, or a zinc aluminum oxide film. If the material of the transparent conductive film 30 is an indium tin oxide film, the mass ratio of In2O3 to SnO2 is in the range of 97:3-99:1; if the material of the transparent conductive film 30 is an indium tungsten oxide film, the mass ratio of In2O3 to W is in the range of 90:10-99.7:0.3; if the material of the transparent conductive film 30 is a zinc aluminum oxide film, the mass ratio of ZnO to Al2O3 is in the range of 90:10-99:1.
[0051] Regardless of the material of the transparent conductive film 30 , the thickness after growth and deposition is in the range of 10-200 nm.
[0052] S3. Depositing a bottom seed layer on the transparent conductive film.
[0053] like Figure 4 As shown, the bottom seed layer 40 is deposited on the transparent conductive film 30, that is, the bottom seed layer 40 is deposited on the prepared cell of the transparent conductive film 30 by using a vacuum deposition process, wherein the bottom seed layer 40 material can be a single metal layer or a metal alloy layer. The material used for the bottom seed layer 40 can be a single metal layer constructed by a single layer of metal such as gold, silver, platinum, copper, palladium, titanium, nickel, tungsten, bismuth, etc., or an alloy metal layer constructed by a combination of two or more metals among gold, silver, platinum, copper, palladium, titanium, nickel, tungsten, and bismuth. Finally, the thickness after preparation ranges from 10 to 200 nm.
[0054] S4. Coating a mask layer on the non-P / N junction electrode area.
[0055] like Figure 5 As shown, a printing coating process, a spray coating process, a spin coating process, or an embossing process is used to prepare a mask layer 50 only on the bottom seed layer 40 at the non-P / N junction electrode area 20, that is, the mask material is directly transferred to the non-P / N junction electrode area 20 to form the mask layer 50.
[0056] The mask layer 50 is then cured. During the curing process, the curing process can be carried out in batches. At this time, the battery cells do not move during the curing process, and the battery cells are carried by a carrier plate to perform batch curing; or the curing process can be carried out continuously. At this time, the battery cells are moved during the curing process. These methods are commonly used processing methods in this field. The heat source during curing can be a single heat source, such as a heat lamp source, hot air drying, a far-infrared heating source, etc.; or a combination of multiple heat sources, which is not specifically limited here. During curing, the curing temperature is 60-200°C, the time is 60-600s, and the thickness of the cured mask layer is 3-50um.
[0057] S5. Depositing metal gate lines in the P / N junction electrode region.
[0058] like Figure 6 As shown, the finished cell is transferred into the electroplating space area in the electroplating equipment, and the current density in the electroplating space area is 5-50A / m 2 The electroplating is continued for 300-900 seconds to form an electroplated metal grid line 60 on the exposed bottom seed layer 40. The width of the prepared metal grid line 60 is in the range of 30-500 um, and the thickness is in the range of 2-5 um. Preferably, the metal grid line 60 is a copper grid line.
[0059] S6, sequentially removing the mask layer, etching back the bottom seed layer, and etching the transparent conductive film.
[0060] like Figure 7 As shown, the mask layer 50 on the non-P / N junction electrode region 20 is first removed, that is, the battery cell is transferred to the removal groove section and the mask layer 50 is etched by wet etching. Accordingly, the etching structure is as shown in FIG. Figure 8 As shown. The cell moves on a rolling conveyor belt, the etched surface is set upward, and the spray nozzle 70 is above the conveyor belt and sprays and etches toward the upper plane of the silicon wafer; of course, the etched surface can also be set downward, and the spray nozzle 70 is correspondingly below the conveyor belt and sprays and etches toward the lower plane of the silicon wafer, all of which are achievable. Regardless of whether the etched surface is set upward or downward, the suitable temperature of the removal solution is 35-55°C, and the concentration range of the spray solution sprayed from the spray nozzle 70 is 1.5-7%. At the same time, the spray pressure range of the solution controlled by the spray nozzle 70 is 0.5-3.5kg / cm 2 , and the spraying time is 30-300s, so that the mask layer 50 on the non-P / N junction electrode area 20 can be completely removed.
[0061] like Fig. 9 As shown, the bottom seed layer is etched back, also using the following method: Figure 8 In the wet etching method shown, the battery cell is transferred to the removal solution tank section to remove the bottom seed layer 40 on the non-P / N junction electrode area. The removal solution is an inorganic acid, which can be a composite solution of any one or more combinations of sulfuric acid, hydrochloric acid, boric acid, phosphoric acid, nitric acid, etc., and its concentration range is 3-8%. If an amino acid additive is added to the inorganic acid removal solution to control the time rate and uniformity, the concentration range of the inorganic acid is required to be 1-2%, which can not only enhance the etching intensity, but also uniformly control the etching efficiency. Accordingly, the temperature of the removal solution is 20-35°C, and the spray pressure range of the spray nozzle 70 is required to be 0.5-2.5kg / cm 2 , and the etching spray time is 30-300s.
[0062] like Fig.10 As shown, the transparent conductive film 30 on the non-P / N junction electrode area is finally etched. Specifically, based on the position of the P / N junction electrode area, the etching paste is applied to the non-P / N junction electrode area on the cell. That is, a layer of etching paste is printed on the position of the transparent conductive film 30 on the cell by screen printing. The etching paste is a uniform etching material obtained by stirring the etching slurry; accordingly, the printing screen uses a 325 mesh, a water-based acid-resistant photosensitive glue screen for screen printing, the printing thickness is 10-20um, and the corresponding printing speed is 200-350mm / s. Of course, different etching and baking processes can also be selected according to the thickness of the coating.
[0063] After the printing and coating is completed, the etching paste is heated to make it react completely with the transparent conductive film 30. The reaction temperature of the etching paste is required to be 130-180°C, and the etching time is required to be 30-300s.
[0064] After that, the battery is controlled to be transmitted to Figure 8 In the removal groove section shown, the transparent conductive film 30 on the non-P / N junction electrode area is removed. The solution used by the spray nozzle 70 is pure water or an aqueous solution containing sodium hydroxide or potassium hydroxide with a concentration of 0.3-2%, so as to rinse and etch the battery cell, so that the transparent conductive film 30 on the non-P / N junction electrode area on the battery cell is completely etched away and rinsed clean.
[0065] S7. Obtain a BC cell with a copper grid structure.
[0066] After the above steps, the obtained battery cell is a BC battery with a copper grid structure prepared by wet etching.
[0067] The entire preparation process is a silver-free production process, which not only has a simple process flow, but also is very easy to control the accuracy of each step; the transparent conductive film 30 and the bottom seed layer 40 prepared by the vacuum deposition process are simpler and more convenient than the nickel seed layer prepared by the chemical vapor deposition process, and can also greatly improve the bonding strength between the metal grid line and the battery cell; and direct patterning followed by electroplating can prepare the metal grid line shape more finely to improve the conductivity of the battery cell.
[0068] A method for preparing a wet-etched copper grid line designed in this application is adopted, and the conventional silicon nitride passivation layer is replaced by a transparent conductive layer and a bottom seed layer; the non-P / N electrode area is prepared by a mature, convenient and highly controllable yellow light patterning process (mask layer covering); the P / N electrode area is then subjected to a metal electroplating deposition process, and after the overall metallization is completed, the mask layer, bottom metal layer and transparent conductive layer on the non-P / N electrode area are removed in sequence; finally, a metal copper fine grid line with a simple process, air operation and complete isolation by wet etching is obtained, thereby improving the isolation effect between the P / N electrode areas. This method not only solves the technical problem of poor adhesion between the metal grid line and the cell, but also improves the bifaciality of the cell module and the grid line conductivity of the P / N electrode through the production of fine-line patterned metal grid lines, thereby ultimately improving the photoelectric conversion efficiency of the BC cell.
[0069] The above detailed description of the embodiments of the present application is only a preferred embodiment of the present application and cannot be considered to limit the scope of implementation of the present application. All equivalent changes and improvements made within the scope of the present application should still fall within the scope of the patent coverage of the present application.
Claims
1. A method for preparing a wet-etched copper grid line, characterized in that the steps include: Obtaining a battery cell having a P / N junction electrode region; Depositing a transparent conductive film on the cell; depositing a bottom seed layer on the transparent conductive film; Applying a mask layer to the non-P / N junction electrode area; Depositing metal gate lines in the P / N junction electrode region; sequentially removing the mask layer, etching back the bottom seed layer, and etching the transparent conductive film; A BC cell with a copper grid structure is obtained.
2. A method for preparing a wet-etched copper grid line according to claim 1, characterized in that: The battery cell with the P / N junction electrode region is prepared with the P / N junction electrode region on the back side of the battery cell.
3. A method for preparing a wet-etched copper grid line according to claim 1 or 2, characterized in that: When preparing the transparent conductive film, a vacuum deposition process is used to deposit a transparent conductive film on the back of the cell having the P / N junction electrode region, and the thickness of the transparent conductive film is in the range of 10-200 nm.
4. A method for preparing a wet-etched copper grid line according to claim 3, characterized in that: The transparent conductive film material is: Indium tin oxide film, wherein the mass ratio of In2O3 to SnO2 is in the range of 97:3-99:1; or, Indium tungsten oxide film, wherein the mass ratio of In2O3 to W is in the range of 90:10-99.7:0.3; or, Zinc oxide aluminum film, wherein the mass ratio of ZnO to Al2O3 ranges from 90:10 to 99:
1.
5. The method for preparing a wet-etched copper grid line according to claim 1, characterized in that: The bottom seed layer is deposited on the transparent conductive film by using a vacuum deposition process to deposit the bottom seed layer on the prepared transparent conductive film cell, wherein the bottom seed layer material can be a single metal layer or a metal alloy layer, and the thickness after preparation ranges from 10 to 200 nm.
6. A method for preparing a wet-etched copper grid line according to any one of claims 1-2, 4-5, characterized in that: A printing coating process, a spray coating process, a spin coating process or an imprinting process is used to prepare a mask layer on the bottom seed layer, and the mask layer is transferred to the non-P / N junction electrode area; and then it is cured; wherein, During curing, the curing temperature is 60-200° C., the time is 60-600s, and the thickness of the cured mask layer is 3-50um.
7. A method for preparing a wet-etched copper grid line according to claim 1, characterized in that: The metal gate line is deposited in the P / N junction electrode region, specifically: controlling the current density of the cell to be 5-50A / m 2 In the electroplating space area, electroplating is continued for 300-900s to form electroplated metal grid lines on the exposed bottom seed layer; the width of the obtained metal grid lines is 30-500um and the thickness is 2-5um.
8. A method for preparing a wet-etched copper grid line according to any one of claims 1-2, 4-5, and 7, characterized in that: When removing the mask layer on the non-P / N junction electrode area, the cell is transferred to the removal tank section. The temperature of the removal solution is 35-55°C, the concentration of the spray solution is 1.5-7%, and the spray pressure of the solution is controlled to be 0.5-3.5kg / cm 2 , spraying time is 30-300s.
9. A method for preparing a wet-etched copper grid line according to claim 8, characterized in that: When etching back the bottom seed layer, the cell is transferred to a removal solution tank section to remove the bottom seed layer on the non-P / N junction electrode area, wherein the removal solution is an inorganic acid with a concentration range of 1-2%; including one or more of sulfuric acid, hydrochloric acid, boric acid, phosphoric acid, and nitric acid; The temperature of the removal solution is 20-35°C and the spray pressure range is 0.5-2.5 kg / cm 2 , and the spraying time is 30-300s.
10. A method for preparing a wet-etched copper grid line according to claim 9, characterized in that: The transparent conductive film on the non-P / N junction electrode area is etched, and based on the position of the P / N junction electrode area, the etching paste is applied to the non-P / N junction electrode area on the battery cell, and the etching temperature is set to 130-180°C, and the etching time is 30-300s; then the battery cell is rinsed with pure water or an aqueous solution containing sodium hydroxide or potassium hydroxide with a concentration of 0.3-2%, and a BC battery with a copper grid structure prepared by wet etching can be obtained.