Preparation method and production equipment of solar cell

Abstract

The invention relates to the technical field of photovoltaics, in particular to a preparation method and production equipment of a solar cell, and the method comprises the steps: carrying out the first development of an exposed photosensitive adhesive layer, so as to form a patterned groove in the photosensitive adhesive layer; spraying a vaporific developing solution to the patterned groove so as to carry out second development on the photosensitive adhesive layer after the first development; performing electroplating in the patterned groove after the second development to form a metal grid line; according to the mode, the second developing device sprays the vaporific developing solution to the graphical groove, the contact area of the developing solution and the graphical groove is increased, the residual glue removing effect is improved, the developing solution is dispersed into small particles, and the small-particle developing solution is more easily dispersed to the connecting position of the side wall and the bottom wall of the graphical groove, so that the developing effect is improved. The effect of removing the residual glue at one end, close to the bottom wall, of the side wall of the patterned groove is improved, the grid line contact area is increased, the grid line binding force is improved, and the product quality of the solar cell is further improved.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to a method for preparing solar cells and production equipment. Background Technology

[0002] In the fabrication process of solar cells, grid electrodes are prepared by metal electroplating, and the grid pattern is laser-printed onto a photosensitive adhesive layer. The photosensitive adhesive layer is then exposed, and the portion with the grid pattern printed on the photosensitive adhesive layer is removed by a developing solution to form grooves on the photosensitive adhesive layer.

[0003] Currently, as battery grid lines become increasingly finer, the width of the grooves is decreasing. After development, residual adhesive remains on the sidewalls of the grooves near their bottom walls, narrowing the contact area between the battery grid lines and the solar cell substrate and reducing the contact area, which is detrimental to improving the bonding strength of the grid lines. At the same time, residual adhesive remains on the bottom walls of the grooves after development, which is also detrimental to improving the bonding strength of the grid lines. Summary of the Invention

[0004] Based on this, this application provides a method and equipment for preparing solar cells to solve the technical problem in the prior art where residual adhesive on the sidewall of the groove near its bottom wall after development and on the bottom wall of the groove are detrimental to improving the bonding force of the grid lines.

[0005] In a first aspect, embodiments of this application provide a method for fabricating a solar cell, characterized in that it includes:

[0006] A solar cell substrate is provided, the surface of which has a metal seed layer;

[0007] A photosensitive emulsion layer is formed on the metal seed layer, a preset pattern is formed on the photosensitive emulsion layer, and the photosensitive emulsion layer with the preset pattern is exposed.

[0008] The exposed photosensitive emulsion layer is first developed to form patterned grooves on the photosensitive emulsion layer;

[0009] A mist of developing solution is sprayed onto the patterned groove to perform a second development on the photosensitive layer after the first development.

[0010] Metal grid lines are formed by electroplating within the patterned grooves after the second development.

[0011] Optionally, in the second development process, the patterned groove is sprayed with a mist-like developing solution with a particle size of 20 μm to 40 μm.

[0012] Optionally, in the first development, a first developing solution is used to perform a first development on the exposed photosensitive layer;

[0013] The first development satisfies at least one of the following (i) to (iv):

[0014] (i) The concentration of developer in the first developer solution is 10 g / L to 20 g / L;

[0015] (ii) The temperature of the first developer is 25℃~35℃;

[0016] (iii) The first developer is sprayed onto the photosensitive adhesive layer at a spray pressure of 0.5 bar to 2.5 bar;

[0017] (iv) The pH value of the first developer is 8 to 13.

[0018] Optionally, in the second development, a second developing solution is used to perform a second development on the photosensitive layer after the first development;

[0019] The second developer is a fresh developer, while the first developer is a reusable developer.

[0020] After spraying a mist-like developing solution onto the patterned grooves to perform a second development on the photosensitive adhesive layer after the first development, the method further includes:

[0021] The second developing solution sprayed during the second developing process overflows into the developing tank used to contain the first developing solution.

[0022] Optionally, the method for fabricating the solar cell further includes:

[0023] The first developing solution is subjected to reverse osmosis membrane treatment;

[0024] The first developer solution is subjected to degreasing treatment.

[0025] Optionally, before electroplating the metal grid lines in the patterned groove after the second development, the method further includes:

[0026] The patterned groove after the second development was cleaned with deionized water.

[0027] The patterned grooves after the second development are cleaned using a cleaning solution containing calcium and magnesium ions.

[0028] Optionally, the first developer and the second developer are both alkaline solutions, and the first developer in the first developer and the second developer in the second developer may be the same or different.

[0029] Optionally, before cleaning the patterned groove after the second development with deionized water, the method further includes:

[0030] The patterned grooves after the second development are cleaned with an air knife to remove the developer remaining in the patterned grooves.

[0031] Secondly, embodiments of this application provide a solar cell manufacturing apparatus, comprising:

[0032] A developing tank is used to hold a solar cell substrate to be developed, the surface of which has a metal seed layer and an exposed photosensitive emulsion layer stacked sequentially.

[0033] The first spraying device is used to spray the first developing solution onto the exposed photosensitive emulsion layer;

[0034] The second spray device is used to spray a mist of the second developing solution onto the exposed photosensitive emulsion layer;

[0035] A reverse osmosis filtration device is used to treat the first developer solution with a reverse osmosis membrane.

[0036] Optionally, the solar cell production equipment further includes:

[0037] An air knife device is used to perform air knife cleaning on the solar cell substrate after the second development.

[0038] A cleaning device is used to clean the solar cell substrate after the second development.

[0039] The solar cell manufacturing method and production equipment of this application embodiment involve first developing the exposed photosensitive adhesive layer to form patterned grooves on the photosensitive adhesive layer; spraying a mist-like developing solution onto the patterned grooves to perform a second development on the photosensitive adhesive layer after the first development; and electroplating to form metal grid lines within the patterned grooves after the second development. Through the above method, the first development erodes and dissolves the unexposed area of ​​the photosensitive adhesive layer to form patterned grooves, and the second development erodes and dissolves residual adhesive at one end of the sidewall of the patterned groove near its bottom wall and at the bottom wall of the patterned groove. The second development sprays a mist-like developing solution onto the patterned groove, increasing the contact area between the developing solution and the patterned groove, which is beneficial for improving the residual adhesive removal effect. Furthermore, since the developing solution is dispersed into small particles, these small particles are more easily dispersed to the junction of the sidewall and bottom wall of the patterned groove, improving the residual adhesive removal effect at the one end of the sidewall of the patterned groove near its bottom wall. This is beneficial for increasing the grid line contact area to improve grid line bonding force, thereby improving the product quality of the solar cell. Attached Figure Description

[0040] Figure 1 This is a schematic flowchart illustrating a method for fabricating a solar cell according to an embodiment of this application.

[0041] Figure 2 This is a schematic diagram of the structure of a solar cell substrate in a method for fabricating a solar cell according to an embodiment of this application.

[0042] Figure 3 This is a scanning electron microscope image of the patterned groove in Embodiment 1 of this application from a first-view perspective.

[0043] Figure 4 This is a scanning electron microscope image of the patterned groove in Comparative Example 1 of this application from a first-view perspective.

[0044] Figure 5 This is a scanning electron microscope image of the patterned groove in Embodiment 1 of this application from a second-view perspective.

[0045] Figure 6 This is a scanning electron microscope image of the patterned groove in Comparative Example 1 of this application from a second-view perspective.

[0046] Figure 7 This is a high-magnification scanning electron microscope image of the texturized silicon wafer after the second development in Embodiment 1 of this application.

[0047] Figure 8 This is a high-magnification scanning electron microscope image of the texturized silicon wafer after development in Comparative Example 1 of this application.

[0048] Figure 9 This is a schematic diagram of the structure of a solar cell according to an embodiment of this application.

[0049] Figure 10 This is a schematic diagram of the structure of a solar cell production equipment according to an embodiment of this application. Detailed Implementation

[0050] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0051] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0053] As used in this article, the description of "a1~a2" means "greater than or equal to a1" and "less than or equal to a2". For example, if x is 0~1, it means: 0≤x≤1.

[0054] like Figures 1 to 8 As shown, this is a method for preparing a solar cell according to one embodiment of this application.

[0055] like Figure 1 As shown, the method for fabricating this solar cell includes the following steps S100 to S500:

[0056] Step S100: Provide a solar cell substrate, the surface of which has a metal seed layer.

[0057] Please see Figure 2 As shown, the solar cell substrate 10 can be, for example, a RESH (Rear Emitter SiHeterojunction) cell substrate. The solar cell substrate 10 includes a silicon wafer substrate 11, a first intrinsic amorphous silicon layer 121 and a second intrinsic amorphous silicon layer 122 respectively stacked on the upper and lower surfaces of the silicon wafer substrate 11, an N-type doped amorphous silicon layer 131 stacked on the side of the first intrinsic amorphous silicon layer 121 away from the silicon wafer substrate 11, a P-type doped amorphous silicon layer 132 stacked on the side of the second intrinsic amorphous silicon layer 122 away from the silicon wafer substrate 11, a first conductive layer 141 stacked on the side of the N-type doped amorphous silicon layer 131 away from the silicon wafer substrate 11, a second conductive layer 142 stacked on the side of the P-type doped amorphous silicon layer 132 away from the silicon wafer substrate 11, a first metal seed layer 151 stacked on the side of the first conductive layer 141 away from the silicon wafer substrate 11, and a second metal seed layer 152 stacked on the side of the second conductive layer 142 away from the silicon wafer substrate 11. The silicon substrate 11 is a silicon wafer with textured upper and lower surfaces respectively.

[0058] Step S200: A photosensitive emulsion layer is formed on the metal seed layer, a preset pattern is formed on the photosensitive emulsion layer, and the photosensitive emulsion layer with the preset pattern is exposed.

[0059] Photosensitive emulsion is coated onto the first metal seed layer 151 and the second metal seed layer 152 to form a photosensitive emulsion layer. This photosensitive emulsion layer can be a negative photosensitive emulsion layer or a positive photosensitive emulsion layer. For example, the thickness of the photosensitive emulsion layer can be 10 to 15 μm.

[0060] If the photosensitive emulsion layer is a negative photosensitive emulsion layer, the preset pattern is a grid pattern. The grid pattern is laser-printed onto the negative photosensitive emulsion layer, covering the grid area of ​​the photosensitive emulsion layer. The non-grid area of ​​the photosensitive emulsion layer is not covered. During exposure, under the action of ultraviolet light, the monomers in the non-grid area of ​​the photosensitive emulsion layer cross-link to form polymers that are not easily soluble in the developer. The grid area of ​​the photosensitive emulsion layer is not affected by ultraviolet light, and the monomers in the grid area of ​​the photosensitive emulsion layer are easily soluble in the developer and are removed in subsequent steps. The resulting patterned grooves correspond to the preset pattern.

[0061] If the photosensitive emulsion layer is a positive photosensitive emulsion layer, the preset pattern is a complementary pattern to the grid pattern. The preset pattern is laser-printed onto the positive photosensitive emulsion layer, covering the non-grid area of ​​the photosensitive emulsion layer. The grid area on the photosensitive emulsion layer is not covered. During exposure, under the action of ultraviolet light, the dissolution inhibitor (e.g., diazonaphthoquinone DNQ) in the grid area of ​​the positive photosensitive emulsion layer decomposes. The non-grid area is not easily dissolved in the developer due to the presence of the dissolution inhibitor, while the grid area is easily dissolved in the developer due to the decomposition of the dissolution inhibitor and is removed in subsequent steps. The resulting patterned groove is complementary to the preset pattern.

[0062] Step S300: Perform a first development on the exposed photosensitive emulsion layer to form patterned grooves on the photosensitive emulsion layer.

[0063] In this process, the photosensitive emulsion layer containing the grid line area can be dissolved using a developing solution, and the photosensitive emulsion layer in the grid line area can be removed to expose the metal seed layer, forming patterned grooves on the photosensitive emulsion layer.

[0064] For example, when the photosensitive adhesive layer is a negative photosensitive adhesive layer, the developing solution can be an alkaline solution. The alkaline reagent is dissolved in water to form the aforementioned alkaline solution, which can be a sodium carbonate (Na2CO3) solution. Under ultraviolet light, the negative photosensitive adhesive layer in the non-grid area undergoes a cross-linking polymerization reaction to form a polymer that is difficult to dissolve in the alkaline solution. The negative photosensitive adhesive layer in the grid area that has not undergone cross-linking polymerization reacts with the alkaline solution and is dissolved and removed.

[0065] Step S400: Spray a mist of developer onto the patterned groove to perform a second development on the photosensitive emulsion layer after the first development.

[0066] Among them, residual adhesive exists on the sidewalls and bottom walls of the patterned groove after the first development. Especially when the width of the patterned groove is narrow, residual adhesive exists on the sidewall of the patterned groove near the bottom wall, making the contact area between the grid line and the metal seed layer of the bottom wall narrower and the contact area between the grid line and the metal seed layer of the bottom wall smaller.

[0067] In the second development process, the developer is sprayed into a mist using a nozzle onto the patterned grooves to remove residual adhesive from the sidewalls and bottom wall of the grooves. Because the developer is dispersed into small particles, these particles are more easily dispersed at the junction of the sidewalls and bottom wall of the patterned groove, depositing on the residual adhesive on the sidewall near the bottom wall. This allows the residual adhesive on the sidewall near the bottom wall of the patterned groove to come into full contact with the developer, thus dissolving and removing the residual adhesive from that sidewall.

[0068] In the first development, a first developing solution is used to perform first development on the exposed photosensitive emulsion layer; in the second development, a second developing solution is used to perform second development on the photosensitive emulsion layer after the first development. The first developing solution includes a first solvent and at least one first developing agent dissolved in the first solvent, and the second developing solution includes a second solvent and at least one second developing agent dissolved in the second solvent. For example, the first solvent and the second solvent can be water, respectively.

[0069] The first developer and the second developer can be of the same type. For example, the first developer and the second developer can be sodium carbonate or potassium carbonate, respectively. For example, the mass concentration of the developer in the first developer solution can be less than or equal to the mass concentration of the developer in the second developer solution.

[0070] The first developer and the second developer can be different types of developers. For example, the first developer and the second developer can be sodium carbonate and potassium carbonate, respectively. For example, the first developer and the second developer can be sodium carbonate and sodium hydroxide, respectively.

[0071] Step S500: Electroplating is performed in the patterned groove after the second development to form metal grid lines.

[0072] In this process, the second developed solar cell substrate 10 is electroplated in a metal salt plating solution to form metal grid lines on a metal seed layer within a patterned groove. Exemplarily, in this embodiment, copper electroplating interconnects can be used to prepare copper grid line electrodes. The metal seed layer can be a copper seed layer. The second developed solar cell substrate 10 is then electroplated in a copper sulfate solution to form copper grid lines on the copper seed layer within the patterned groove. In some embodiments, after forming the copper grid lines, tin grid lines can be further electroplated on the copper grid lines, and these tin grid lines can serve as a protective layer for the copper grid lines.

[0073] In this embodiment, the first developing process etches and dissolves the unexposed area of ​​the photosensitive emulsion layer to form a patterned groove. The second developing process etches and dissolves the sidewall of the patterned groove near its bottom wall and the residual emulsion on the bottom wall of the patterned groove. The second developing process sprays a mist of developing solution onto the patterned groove, increasing the contact area between the developing solution and the patterned groove, which is beneficial for improving the removal of residual emulsion. Furthermore, since the developing solution is dispersed into small particles, these small particles are more easily dispersed at the junction of the sidewall and bottom wall of the patterned groove, improving the removal of residual emulsion on the sidewall near its bottom wall. This is beneficial for increasing the contact area of ​​the grid lines to improve the grid line adhesion, thereby improving the product quality of the solar cell. Moreover, because the residual emulsion on the sidewall near its bottom wall of the patterned groove is removed, the developing solution in the second developing process reacts more easily with the residual photosensitive emulsion on the bottom wall of the patterned groove, improving the dissolution and removal effect of the residual emulsion on the bottom wall of the patterned groove.

[0074] In one embodiment, during the second development process, a mist-like developer with a particle size of 20 μm to 40 μm is sprayed onto the patterned groove. In this embodiment, controlling the particle size of the developer within the aforementioned range further improves the removal effect of residual adhesive on the sidewall of the patterned groove near its bottom wall.

[0075] In one implementation, the first developer and the second developer can be of the same type. The second developer is a fresh developer, and the first developer is a reusable developer, i.e., the first developer is an old developer.

[0076] Accordingly, after step S400, the following step is also included: allowing the second developing solution sprayed during the second developing process to overflow into the developing tank used to contain the first developing solution.

[0077] In this embodiment, during repeated use of the first developer, as the amount of dissolved photosensitive emulsion increases, the pH value of the first developer decreases, the developer concentration decreases, and the developing effect of the first developer gradually declines. The second developer uses a fresh developer solution, which can further improve the removal of residual emulsion from the patterned grooves. Simultaneously, combining the fresh developer solution used in the second development with the first developer solution helps to increase both the pH value and the developer concentration of the first developer solution, thereby improving the developing effect of the first development and extending the usage time of the first developer solution.

[0078] As one implementation method, the first development employs a chain development process.

[0079] In some embodiments, during the first developing step, the concentration of the developer in the first developing solution is 10 g / L to 20 g / L. Exemplarily, the concentration of the developer in the first developing solution can be, but is not limited to, 10 g / L, 12 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, or 20 g / L.

[0080] In some embodiments, the temperature of the first developing solution in the first developing step is 25°C to 35°C.

[0081] In some embodiments, during the first developing step, a first developer is sprayed onto the photosensitive emulsion layer at a spray pressure of 0.5 bar to 2.5 bar. Exemplarily, the spray pressure of the first developer can be, but is not limited to, 0.5 bar, 0.6 bar, 0.8 bar, 1.0 bar, 1.3 bar, 1.5 bar, 1.8 bar, 2.0 bar, 2.2 bar, or 2.5 bar.

[0082] In some embodiments, the pH value of the first developer in the first developing step is 8 to 13. Exemplarily, the pH value of the first developer can be, but is not limited to, 8, 8.5, 9, 9.2, 9.5, 10, 11, 12, or 13.

[0083] In this embodiment, controlling the conditions of the first development can improve the first development effect.

[0084] As one implementation method, the solar cell fabrication method of this embodiment further includes the following steps:

[0085] Step S301: Treat the first developer solution with a reverse osmosis membrane.

[0086] In this embodiment, the reverse osmosis membrane treatment can adsorb the organic membrane reactants contained in the aged first developer, thereby purifying the first developer and improving the first developing effect.

[0087] As one implementation method, the solar cell fabrication method of this embodiment further includes the following steps:

[0088] Step S302: Degrease the first developer.

[0089] In this embodiment, with repeated use of the first developer, the photosensitive emulsion reacts with the developing components to produce organic oil-like suspended matter in the first developer. If this organic oil-like suspended matter adheres to the patterned grooves, it will reduce the bonding force between the grid lines and the metal seed layer. An oil-absorbing device is provided in the flow channel of the first developer to absorb the organic oil-like suspended matter, thereby purifying the first developer and improving the first developing effect. For example, the oil-absorbing device can be an oil-absorbing cotton.

[0090] As one implementation method, the solar cell fabrication method of this embodiment further includes the following steps after step S400:

[0091] Step S401: Clean the patterned groove after the second development with deionized water.

[0092] The patterned grooves are cleaned using deionized water to remove substances formed by the reaction and dissolution of residual adhesive in the grooves, as well as to remove any residual second developer. For example, deionized water at 20°C to 35°C can be sprayed into the cleaning tank containing the solar cell substrate, with a spray pressure of 0.5 bar to 2.5 bar.

[0093] Step S402: Clean the patterned groove after the second development using a cleaning solution containing calcium and magnesium ions.

[0094] The calcium and magnesium ions in the cleaning solution can react with residual adhesive in the patterned grooves to further remove it. Cleaning the patterned grooves with deionized water before using the cleaning solution prevents the residual second developer from reacting with calcium or magnesium ions to form solid deposits. For example, calcium ions can react with sodium carbonate in the second developer to form calcium carbonate.

[0095] In some embodiments, the concentration of calcium ions in the cleaning solution can be 0.01 g / L to 0.05 g / mL, the concentration of magnesium ions in the cleaning solution can be 0.01 g / L to 0.05 g / mL, and the temperature of the cleaning solution can be 25 to 35°C. For example, the cleaning solution can be tap water.

[0096] In some embodiments, the method for fabricating solar cells in this embodiment further includes the following steps after step S400 and before step S401:

[0097] Step S401': Perform air knife cleaning on the patterned groove after the second development to remove the developer solution remaining in the patterned groove.

[0098] In this embodiment, an air knife is used to blow away the developer residue in the patterned grooves, followed by cleaning with deionized water and cleaning solution in sequence. This can further improve the cleaning effect and prevent the developer from reacting with calcium and magnesium ions in the cleaning solution.

[0099] As one implementation method, step S100 specifically includes the following steps:

[0100] Step S101: The silicon wafer substrate 11 is texturized and cleaned to form a uniform "positive pyramid" textured surface on the surface of the silicon wafer substrate 11.

[0101] The base dimension (side length of the square base) of the pyramid structure with a velvety surface can be 2 to 8 μm.

[0102] Step S102: A first intrinsic amorphous silicon layer 121 and an N-type doped amorphous silicon layer 131 are deposited on the upper surface of the texturized silicon wafer substrate 11 using a PECVD (plasma enhanced chemical vapor deposition) plasma deposition equipment. A second intrinsic amorphous silicon layer 122 and a P-type doped amorphous silicon layer 132 are deposited sequentially on the lower surface of the texturized silicon wafer substrate 11 using a PECVD plasma deposition equipment.

[0103] The thickness of the first intrinsic amorphous silicon layer 121 can be 3–6 nm, the thickness of the second intrinsic amorphous silicon layer 122 can be 3–9 nm, the thickness of the N-type doped amorphous silicon layer 131 can be 5–10 nm, and the thickness of the P-type doped amorphous silicon layer 132 can be 5–15 nm.

[0104] Step S103: A first conductive layer 141 and a second conductive layer 142 are deposited on an N-type doped amorphous silicon layer 131 and a P-type doped amorphous silicon layer 132 respectively using a PVD (Physical Vapor Deposition) magnetron sputtering equipment.

[0105] The first conductive layer 141 and the second conductive layer 142 can each be an ITO (Indium Tin Oxide) transparent conductive film. The thicknesses of the first conductive layer 141 and the second conductive layer 142 can each be 90–110 nm.

[0106] Step S104: Deposit the first metal seed layer 151 and the second metal seed layer 152 on the first conductive layer 141 and the second conductive layer 142 respectively using a PVD magnetron sputtering device.

[0107] The thicknesses of the first metal seed layer 151 and the second metal seed layer 152 can be 100-250 nm, respectively.

[0108] As one implementation method, the solar cell fabrication method of this embodiment further includes the following steps after step S400 and before step S500:

[0109] Step S403: Wrap the four edges and corners of the second developed solar cell substrate 10 with edge-sealing adhesive. The width of the edge-sealing adhesive is less than or equal to 50 μm and the thickness of the edge-sealing adhesive is 10 to 15 μm.

[0110] Accordingly, the method for fabricating solar cells in this embodiment further includes the following steps after step S500:

[0111] Step S501, Film Removal and Etching Back: Remove all the edge-sealing adhesive and mask material in a strong alkaline solution, and remove the metal seed layer in the non-gate area in an acidic etching solution.

[0112] In this process, only metal grid lines remain on the surfaces of the first conductive layer 141 and the second conductive layer 142, respectively.

[0113] The strongly alkaline solution can be a sodium hydroxide (NaOH) solution or a potassium hydroxide (KOH) solution.

[0114] Step S502, light injection: The solar cell substrate 10 after film removal and re-etching is subjected to light injection treatment at a temperature of 200℃~220℃ for 60s~120s.

[0115] In step S503, the solar cell substrate 10 with light injection is immersed in tin melt to form a layer of pure tin 100-200 nm thick covering the surface of the metal grid lines, thus obtaining the solar cell.

[0116] The tin gate wire serves to protect the metal gate wire from oxidation, and it also provides a substrate for soldering.

[0117] One embodiment of this application also provides a solar cell, which is prepared using the solar cell preparation method described above.

[0118] As one implementation method, please refer to Figure 9 As shown, the solar cell 20 includes a silicon substrate 11, a first intrinsic amorphous silicon layer 121 and a second intrinsic amorphous silicon layer 122 respectively stacked on the upper and lower surfaces of the silicon substrate 11, an N-type doped amorphous silicon layer 131 stacked on the side of the first intrinsic amorphous silicon layer 121 away from the silicon substrate 11, a P-type doped amorphous silicon layer 132 stacked on the side of the second intrinsic amorphous silicon layer 122 away from the silicon substrate 11, a first conductive layer 141 stacked on the side of the N-type doped amorphous silicon layer 131 away from the silicon substrate 11, a second conductive layer 142 stacked on the side of the P-type doped amorphous silicon layer 132 away from the silicon substrate 11, and metal grid electrodes 16 respectively stacked on the side of the first conductive layer 141 away from the silicon substrate 11 and the side of the second conductive layer 142 away from the silicon substrate 11.

[0119] In one embodiment, the silicon substrate 11 is a silicon wafer with textured upper and lower surfaces respectively.

[0120] In one embodiment, the metal gate electrode 16 includes a metal seed layer 161, a metal gate line 162, and a protective layer 163 stacked sequentially. For example, the metal seed layer 161 may be a copper seed layer, the metal gate line 162 may be a copper gate line, and the protective layer 163 may be a tin metal layer.

[0121] One embodiment of this application provides a solar cell manufacturing apparatus; please refer to [link / reference]. Figure 10 As shown, the solar cell production equipment 200 includes: a developing tank 21, a first spraying device 221, a second spraying device 222, and a reverse osmosis filtration device 23. Using the solar cell production equipment 200 of this embodiment, solar cells are prepared according to the steps of the solar cell preparation method of the above-described embodiments or implementations.

[0122] The developing tank 21 is used to hold the solar cell substrate to be developed. The surface of the solar cell substrate has a metal seed layer and an exposed photosensitive emulsion layer stacked in sequence. A preset pattern is formed on the photosensitive emulsion layer of the solar cell substrate, and the photosensitive emulsion layer with the preset pattern is exposed.

[0123] The first spraying device 221 is used to spray the first developing solution onto the exposed photosensitive emulsion layer to perform the first development on the exposed photosensitive emulsion layer, so as to form patterned grooves on the photosensitive emulsion layer.

[0124] The second spray device 222 is used to spray a mist of second developing solution onto the exposed photosensitive emulsion layer, thereby performing a second development on the photosensitive emulsion layer after the first development by spraying the mist of developing solution onto the patterned groove.

[0125] The reverse osmosis filtration device 23 is used to treat the first developer solution with a reverse osmosis membrane. The reverse osmosis filtration device 23 can adsorb the organic membrane reactants contained in the aged first developer solution to purify the first developer solution. The first developer solution treated by the reverse osmosis filtration device 23 is sprayed onto the photosensitive adhesive layer by the first spraying device 221 to perform the first development on the photosensitive adhesive layer, which can improve the first development effect.

[0126] In this embodiment, a first spraying device is used to first develop and etch the unexposed area of ​​the photosensitive adhesive layer to form a patterned groove. A second spraying device is used to second develop and etch the sidewall of the patterned groove near its bottom wall and the residual adhesive on the bottom wall of the patterned groove. The second developing device sprays a mist of developing solution onto the patterned groove, which increases the contact area between the developing solution and the patterned groove, thus improving the residual adhesive removal effect. Furthermore, the reverse osmosis filtration device can adsorb the organic film reactants contained in the aged first developing solution, thereby improving the first developing effect.

[0127] In one embodiment, the solar cell production equipment 200 also includes an air knife device 24 and a cleaning device 25.

[0128] The air knife device 24 is used to clean the solar cell substrate after the second development. By using the air knife device 24 to blow away the developer remaining in the patterned grooves, followed by water rinsing, the cleaning effect can be further improved.

[0129] The cleaning device 25 is used to wash the solar cell substrate after the second development with water. Specifically, the cleaning device 25 can first use deionization to clean the patterned grooves, and then use a cleaning solution containing calcium and magnesium ions to clean the patterned grooves after the second development.

[0130] The cleaning device 25 includes a first cleaning unit 251 and a second cleaning unit 252. The first cleaning unit 251 uses deionization to clean the patterned grooves, and the second cleaning unit 252 uses a cleaning solution containing calcium ions and magnesium ions to clean the second developed patterned grooves.

[0131] The first cleaning unit 251 performs sampling deionization cleaning to remove substances formed by the reaction and dissolution of residual adhesive in the patterned grooves, as well as to remove the second developer remaining in the patterned grooves. For example, deionized water at 20°C to 35°C can be sprayed into a cleaning tank containing a solar cell substrate, with a spray pressure of 0.5 bar to 2.5 bar.

[0132] The calcium and magnesium ions in the cleaning solution of the second cleaning unit 252 can react with the residual adhesive in the patterned grooves to further remove the adhesive. Cleaning the patterned grooves with deionized water before using the cleaning solution can prevent the second developer remaining in the patterned grooves from reacting with calcium or magnesium ions to form solid deposits. For example, calcium ions can react with sodium carbonate in the second developer to form calcium carbonate.

[0133] Furthermore, by using an air knife device 24 to blow away the developer residue remaining in the patterned grooves, followed by sequential cleaning with deionized water and cleaning solution, the cleaning effect can be further improved, and the reaction between the developer and calcium and magnesium ions in the cleaning solution can be prevented.

[0134] One embodiment of this application also provides a battery assembly, including the solar cell described above.

[0135] The present application will be further illustrated below through specific embodiments and comparative examples.

[0136] Example 1

[0137] This embodiment provides a method for fabricating a solar cell, including the following steps:

[0138] Step (1) The silicon wafer substrate 11 is texturized and cleaned to form a uniform "positive pyramid" textured surface on the surface of the silicon wafer substrate 11.

[0139] The base dimension (side length of the square base) of the pyramid structure with a velvety surface can be 2 to 8 μm.

[0140] Step (2) involves depositing a first intrinsic amorphous silicon layer 121 and an N-type doped amorphous silicon layer 131 on the upper surface of the texturized silicon substrate 11 using a PECVD (plasma enhanced chemical vapor deposition) plasma deposition equipment. Then, a second intrinsic amorphous silicon layer 122 and a P-type doped amorphous silicon layer 132 are deposited sequentially on the lower surface of the texturized silicon substrate 11 using the same PECVD equipment. The thickness of the first intrinsic amorphous silicon layer 121 can be 3–6 nm, the thickness of the second intrinsic amorphous silicon layer 122 can be 3–9 nm, the thickness of the N-type doped amorphous silicon layer 131 can be 5–10 nm, and the thickness of the P-type doped amorphous silicon layer 132 can be 5–15 nm.

[0141] Step (3) involves depositing a first conductive layer 141 and a second conductive layer 142 on the N-type doped amorphous silicon layer 131 and the P-type doped amorphous silicon layer 132 using a PVD (Physical Vapor Deposition) magnetron sputtering apparatus. The first conductive layer 141 and the second conductive layer 142 can each be a transparent conductive film of ITO (Indium Tin Oxide). The thicknesses of the first conductive layer 141 and the second conductive layer 142 can be 90–110 nm, respectively.

[0142] Step (4) A first metal seed layer 151 and a second metal seed layer 152 are deposited on the first conductive layer 141 and the second conductive layer 142 using a PVD magnetron sputtering device. The first metal seed layer 151 and the second metal seed layer 152 are copper seed layers, and the thicknesses of the first metal seed layer 151 and the second metal seed layer 152 can be 100-250 nm, respectively.

[0143] Step (5) Coating: Photosensitive emulsion is coated on the first metal seed layer 151 and the second metal seed layer 152 respectively to completely cover the copper seed layer. The thickness of the photosensitive emulsion layer is controlled at 10-15 μm.

[0144] Step (6) Laser printing and exposure: The designed grid pattern is laser-printed onto the photosensitive adhesive layer and then exposed. The photosensitive adhesive layer will change when exposed to light (non-grid area is exposed to light), which can distinguish it from the unexposed area (i.e., the grid area).

[0145] Step (7) Development process flow:

[0146] (7-1) First stage development: The unexposed photosensitive emulsion layer (raster area) is cleaned and removed using a sodium carbonate (Na2CO3) solution. The sodium carbonate concentration is controlled at 10-20 g / L, the solution temperature is 25℃-35℃, the nozzle pressure is 0.5 bar-2.5 bar, and the solution pH value is controlled between 8 and 13. The sodium carbonate solution reacts with the unexposed photosensitive emulsion layer to form preliminary patterned grooves.

[0147] (7-2) Second stage "spray" new developer overflow section: The nozzle is equipped with a newly prepared sodium carbonate solution, and the unexposed photosensitive emulsion layer (grid area) is evenly sprayed with 20-40μm mist developer solution to remove the unexposed photosensitive emulsion that cannot be removed due to the aging of the first stage developer solution. At the same time, it overflows into the first stage developer tank to replace the old solution and extend the life of the solution.

[0148] (7-3) External reverse osmosis filtration system: adsorbs organic membrane reactants in the aged developer solution of the first stage of development, purifies the solution, and improves the development effect.

[0149] (7-4) Air cutting: Using an air cutting device to blow away most of the developer solution used in the second section on the surface of the battery substrate.

[0150] (7-5) Cleaning: First, use deionized water to clean the surface of the battery substrate to dilute the developer; then use tap water at 35°C to clean the surface of the battery substrate. The residual adhesive in the patterned grooves is removed by the reaction of calcium and magnesium ions with the adhesive; then clean the surface of the battery substrate with deionized water to reduce the introduction of ionic contaminants into the next process.

[0151] (7-6) Drying: The design incorporates stainless steel magnetic rollers to prevent dust from contaminating the battery substrate due to friction.

[0152] Step (8) Edge wrapping: Wrap the four corner edges and corner positions with edge wrapping adhesive. The width of the edge wrapping adhesive is less than or equal to 50μm and the thickness of the edge wrapping adhesive is 10-15μm.

[0153] Step (9) Electroplating: Electroplating copper grid lines in copper sulfate electroplating solution, with the height of the copper grid lines controlled at 8-10 μm; electroplating tin grid lines in tin methanesulfonate electroplating solution, with the height of the tin grid lines controlled at 2-4 μm.

[0154] Step (10) Removal and Etching: First, remove all photosensitive emulsion and mask material in an alkaline solution (NaOH, KOH, etc.). Second, remove the copper seed layer in the non-grid area in a dilute sulfuric acid solution. Finally, leave only the copper grid lines on the surface of the first conductive layer and the second conductive layer.

[0155] Step (11) Photoinjection: The battery substrate after film removal and re-etching is subjected to photoinjection treatment at a temperature of 200℃~220℃ for 60s~120s.

[0156] Step (12) Tinning: The light-injected wafer is immersed in tinning solution to form a layer of pure tin 100-200nm thick covering the surface of the copper gate line, which protects the gate line from oxidation and provides a solderable substrate.

[0157] Step (13): Complete the cell fabrication and perform IV testing on the electrical performance.

[0158] Comparative Example 1

[0159] This embodiment provides a method for fabricating a solar cell, including the following steps:

[0160] Step (1) The silicon wafer substrate 11 is texturized and cleaned to form a uniform "positive pyramid" textured surface on the surface of the silicon wafer substrate 11.

[0161] The base dimension (side length of the square base) of the pyramid structure with a velvety surface can be 2 to 8 μm.

[0162] Step (2) involves depositing a first intrinsic amorphous silicon layer 121 and an N-type doped amorphous silicon layer 131 on the upper surface of the texturized silicon substrate 11 using a PECVD (plasma enhanced chemical vapor deposition) plasma deposition equipment. Then, a second intrinsic amorphous silicon layer 122 and a P-type doped amorphous silicon layer 132 are deposited sequentially on the lower surface of the texturized silicon substrate 11 using the same PECVD equipment. The thickness of the first intrinsic amorphous silicon layer 121 can be 3–6 nm, the thickness of the second intrinsic amorphous silicon layer 122 can be 3–9 nm, the thickness of the N-type doped amorphous silicon layer 131 can be 5–10 nm, and the thickness of the P-type doped amorphous silicon layer 132 can be 5–15 nm.

[0163] Step (3) involves depositing a first conductive layer 141 and a second conductive layer 142 on the N-type doped amorphous silicon layer 131 and the P-type doped amorphous silicon layer 132 using a PVD (Physical Vapor Deposition) magnetron sputtering apparatus. The first conductive layer 141 and the second conductive layer 142 can each be a transparent conductive film of ITO (Indium Tin Oxide). The thicknesses of the first conductive layer 141 and the second conductive layer 142 can be 90–110 nm, respectively.

[0164] Step (4) A first metal seed layer 151 and a second metal seed layer 152 are deposited on the first conductive layer 141 and the second conductive layer 142 using a PVD magnetron sputtering device. The first metal seed layer 151 and the second metal seed layer 152 are copper seed layers, and the thicknesses of the first metal seed layer 151 and the second metal seed layer 152 can be 100-250 nm, respectively.

[0165] Step (5) Coating: Photosensitive emulsion is coated on the first metal seed layer 151 and the second metal seed layer 152 respectively to completely cover the copper seed layer. The thickness of the photosensitive emulsion layer is controlled at 10-15 μm.

[0166] Step (6) Laser printing and exposure: The designed grid pattern is laser-printed onto the photosensitive adhesive layer and then exposed. The photosensitive adhesive layer will change when exposed to light (non-grid area is exposed to light), which can distinguish it from the unexposed area (i.e., the grid area).

[0167] Step (7) Development process flow:

[0168] (7-1) First stage development: The unexposed photosensitive emulsion layer (raster area) is cleaned and removed using a sodium carbonate (Na2CO3) solution. The sodium carbonate concentration is controlled at 10-20 g / L, the solution temperature is 25℃-35℃, the nozzle pressure is 0.5 bar-2.5 bar, and the solution pH value is controlled between 8 and 13. The sodium carbonate solution reacts with the unexposed photosensitive emulsion layer to form preliminary patterned grooves.

[0169] (7-2) Second stage development: The unexposed photosensitive adhesive layer (raster area) is cleaned and removed using a sodium carbonate (Na2CO3) solution. The sodium carbonate concentration is controlled at 10-20 g / L, the solution temperature is 25℃-35℃, the nozzle pressure is 0.5 bar-2.5 bar, and the solution pH value is controlled between 8 and 13. The sodium carbonate solution reacts with the residual adhesive in the patterned grooves to remove the residual adhesive.

[0170] Step (8) Edge wrapping: Wrap the four corner edges and corner positions with edge wrapping adhesive. The width of the edge wrapping adhesive is less than or equal to 50μm and the thickness of the edge wrapping adhesive is 10-15μm.

[0171] Step (9) Electroplating: Electroplating copper grid lines in copper sulfate electroplating solution, with the height of the copper grid lines controlled at 8-10 μm; electroplating tin grid lines in tin methanesulfonate electroplating solution, with the height of the tin grid lines controlled at 2-4 μm.

[0172] Step (10) Removal and Etching: First, remove all photosensitive emulsion and mask material in an alkaline solution (NaOH, KOH, etc.). Second, remove the copper seed layer in the non-grid area in a dilute sulfuric acid solution. Finally, leave only the copper grid lines on the surface of the first conductive layer and the second conductive layer.

[0173] Step (11) Photoinjection: The battery substrate after film removal and re-etching is subjected to photoinjection treatment at a temperature of 200℃~220℃ for 60s~120s.

[0174] Step (12) Tinning: The light-injected wafer is immersed in tinning solution to form a layer of pure tin 100-200nm thick covering the surface of the copper gate line, which protects the gate line from oxidation and provides a solderable substrate.

[0175] Step (13): Complete the cell fabrication and perform IV testing on the electrical performance.

[0176] Result comparison:

[0177] The dried patterned grooves obtained in Example 1 and Comparative Example 1 were tested using scanning electron microscopy (SEM) at a first-viewing angle. The test results are shown in [link to SEM]. Figure 3 and Figure 4 As shown.

[0178] like Figure 3 and Figure 4 As shown, the sidewall of the patterned groove formed in Example 1 is closer to the bottom wall. Figure 3 (Selected by the white dashed line in the middle) No residual photosensitive adhesive was found, and the bottom wall of the patterned groove was relatively wide; while the side wall of the patterned groove prepared in Comparative Example 1 was closer to the bottom wall ( Figure 4 (The area highlighted by the white dashed line) contains residual photosensitive adhesive, and the bottom wall of the patterned groove is relatively narrow. In Example 1, the patterned groove completely removes the residual photosensitive adhesive from the sidewall closest to the bottom wall and relatively widens the bottom wall. This widening makes it easier for the developing solution to react with and dissolve the remaining photosensitive adhesive on the bottom wall. Thus, under the same grid line width requirement, the contact area between the electroplated copper grid lines and the copper seed layer in Example 1 is larger, ensuring lower contact resistance between the copper grid lines and the solar cell, improving the fill factor of the solar cell, and thus increasing the cell conversion efficiency.

[0179] The dried patterned grooves obtained in Example 1 and Comparative Example 1 were subjected to scanning electron microscopy (SEM) tests from a second-view perspective. The test results are shown in [link to SEM]. Figure 5 and Figure 6 As shown.

[0180] X-ray energy dispersive spectroscopy (EDS) was used to test the bottom walls of the dried patterned grooves obtained in Example 1 and Comparative Example 1, respectively. Figure 5 and Figure 6The area highlighted by the black dashed rectangle is the EDS test area. The test results are shown in Table 1 below.

[0181] Table 1 Comparison of EDS test results of the patterned grooves obtained in Example 1 and Comparative Example 1

[0182]

[0183] like Figure 5 and Figure 6 As shown, from a top-down view, the bottom and side walls of the patterned groove prepared in Example 1 had no residual photosensitive adhesive, while the bottom and side walls of the patterned groove prepared in Comparative Example 1 had residual photosensitive adhesive, especially noticeable on the side walls of the patterned groove in Comparative Example 1. According to Table 1, EDS testing showed that the carbon content ("C") at the center of the bottom wall of the patterned groove prepared in Comparative Example 1 reached 55.84%, while the bottom walls of the patterned groove prepared in Example 1 had no residual photosensitive adhesive on either side. Furthermore, the carbon content ("C") at the center of the bottom wall of the patterned groove in Example 1 was only 9.7%, indicating that the residual adhesive removal effect of the bottom wall of the patterned groove prepared in Example 1 was better.

[0184] Comparison of residual adhesive on textured surfaces: High-magnification scanning electron microscopy (SEM) tests were performed on the texturized silicon wafers prepared in Example 1 and Comparative Example 1, respectively. The test results are shown in [link to SEM]. Figure 7 and Figure 8 As shown.

[0185] like Figure 7 and Figure 8 As shown, high-magnification SEM observation of the textured silicon wafer revealed that a large amount of photosensitive adhesive remained on the surface of the pyramid in Comparative Example 1 and could not be completely removed by development; while the pyramid surface in Example 1 had no photosensitive adhesive residue, further demonstrating that the preparation method of Example 1 has an excellent effect on removing residual adhesive.

[0186] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0187] The above embodiments merely illustrate preferred implementations of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for fabricating a solar cell, characterized in that, include: A solar cell substrate is provided, the surface of which has a metal seed layer; A photosensitive emulsion layer is formed on the metal seed layer, a preset pattern is formed on the photosensitive emulsion layer, and the photosensitive emulsion layer with the preset pattern is exposed. The exposed photosensitive emulsion layer is first developed to form patterned grooves on the photosensitive emulsion layer; A mist of developing solution is sprayed onto the patterned groove to perform a second development on the photosensitive layer after the first development. Metal grid lines are formed by electroplating within the patterned grooves after the second development.

2. The method for preparing a solar cell according to claim 1, characterized in that, In the second development process, a mist-like developing solution with a particle size of 20 μm to 40 μm is sprayed onto the patterned groove.

3. The method for preparing a solar cell according to claim 1, characterized in that, In the first development, a first developing solution is used to perform a first development on the exposed photosensitive emulsion layer; The first development satisfies at least one of the following (i) to (iv): (i) The concentration of developer in the first developer solution is 10 g / L to 20 g / L; (ii) The temperature of the first developer is 25℃~35℃; (iii) The first developer is sprayed onto the photosensitive adhesive layer at a spray pressure of 0.5 bar to 2.5 bar; (iv) The pH value of the first developer is 8 to 13.

4. The method for preparing a solar cell according to claim 3, characterized in that, In the second development, a second developing solution is used to perform a second development on the photosensitive layer after the first development; The second developer is a fresh developer, while the first developer is a reusable developer. After spraying a mist-like developing solution onto the patterned grooves to perform a second development on the photosensitive adhesive layer after the first development, the method further includes: The second developing solution sprayed during the second developing process overflows into the developing tank used to contain the first developing solution.

5. The method for preparing a solar cell according to claim 4, characterized in that, The method for preparing the solar cell further includes: The first developing solution is subjected to reverse osmosis membrane treatment; The first developer solution is subjected to degreasing treatment.

6. The method for preparing a solar cell according to claim 4, characterized in that, The first developing solution and the second developing solution are both alkaline solutions, and the first developing agent in the first developing solution and the second developing agent in the second developing solution are the same or different.

7. The method for preparing a solar cell according to claim 1, characterized in that, Before electroplating to form metal grid lines in the patterned groove after the second development, the process further includes: The patterned groove after the second development was cleaned with deionized water. The patterned grooves after the second development are cleaned using a cleaning solution containing calcium and magnesium ions.

8. The method for preparing a solar cell according to claim 7, characterized in that, Before cleaning the patterned grooves after the second development with deionized water, the method further includes: The patterned grooves after the second development are cleaned with an air knife to remove the developer remaining in the patterned grooves.

9. A solar cell manufacturing apparatus, characterized in that, include: A developing tank is used to hold a solar cell substrate to be developed, the surface of which has a metal seed layer and an exposed photosensitive emulsion layer stacked sequentially. The first spraying device is used to spray the first developing solution onto the exposed photosensitive emulsion layer; The second spray device is used to spray a mist of the second developing solution onto the exposed photosensitive emulsion layer; A reverse osmosis filtration device is used to treat the first developer solution with a reverse osmosis membrane.

10. The solar cell production equipment according to claim 9, characterized in that, The solar cell production equipment also includes: An air knife device is used to perform air knife cleaning on the solar cell substrate after the second development. A cleaning device is used to clean the solar cell substrate after the second development.

Images