Method for screen printing on substrate, printing device, and solar cell

Abstract

Disclosed are a method for screen printing on a substrate, a printing device, and a solar cell. The method comprises: conveying to a printing station a substrate (1) on which printing is to be performed; moving a screen (2) to a predetermined printing position, the screen being located above the substrate on which printing is to be performed, and a paste (4) being located on the screen; and controlling a printing apparatus to move on the screen to perform paste deposition at least twice on the upper surface of the same substrate on which printing is to be performed, so that printing is completed. The method improves the printing operation efficiency and obtains a good printing effect.

Description

Method for screen printing on substrate, printing equipment and solar cell Technical Field

[0001] The present invention relates to a battery printing technology, in particular to a method for screen printing on a substrate, a printing device and a solar cell. Background Art

[0002] Currently, silicon-based heterojunction solar cells are a common high-efficiency solar cell technology. The transparent conductive film layer TCO serves as a lateral carrier transport layer and is an indispensable part of silicon-based heterojunction solar cells. Silver grid electrodes are formed on the transparent conductive film layer by screen printing. The silver grid electrodes are usually made using overprinting technology. In order to obtain grid lines with a higher aspect ratio, the existing technology uses two printing stations. After the first printing on the transparent conductive film layer using a screen, it enters the second printing station. At the second printing station, a second printing is performed on the transparent conductive film layer using a screen again to form a secondary deposition slurry. After two printings, the grid lines have a higher aspect ratio. The so-called aspect ratio refers to the ratio of the height to the width of the grid lines. The aspect ratio of the grid lines prepared by screen printing in the existing technology is usually below 24%. The screen printing of the existing technology has a long operation cycle and low efficiency.

[0003] Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for screen printing on a substrate, a printing device and a solar cell, so as to improve the printing operation efficiency and obtain good printing effects.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for screen printing on a substrate, comprising:

[0007] Transporting the substrate to be printed to the printing station;

[0008] The screen is moved to a predetermined printing position, the screen is positioned above the substrate to be printed, and the slurry is positioned on the screen;

[0009] The printing device is controlled to move on the screen, and the slurry is deposited at least twice on the surface of the same substrate to be printed to complete printing.

[0010] As a preferred example, the slurry is deposited twice on the same substrate to be printed to complete printing.

[0011] As a preferred example, the controlling the printing device to move on the screen includes: controlling the printing device to move from a first side of the screen to a second side opposite to the first side, completing a first slurry deposition, and forming a first deposited slurry on the upper surface of the substrate to be printed; controlling the printing device to move from the second side of the screen to the first side, completing a second slurry deposition, and forming a second deposited slurry on the upper surface of the substrate to be printed, and the second deposited slurry is at least partially stacked on the first deposited slurry.

[0012] As a preferred example, the printing device includes a first processing head assembly provided with a scraper and a second processing head assembly provided with a scraper; during the first slurry deposition, the scraper of the first processing head assembly is lowered to contact the surface of the screen, and the scraper of the second processing head assembly is not in contact with the surface of the screen, and the first slurry deposition is completed using the scraper of the first processing head assembly; during the second slurry deposition, the scraper of the second processing head assembly is lowered to contact the surface of the screen; the scraper of the first processing head assembly is raised to not contact the surface of the screen; and the second slurry deposition is completed using the scraper of the second processing head assembly.

[0013] As a preferred example, the amount of slurry deposited on the substrate to be printed in the first slurry deposition is less than the amount of slurry deposited on the substrate to be printed in the second slurry deposition.

[0014] As a preferred example, the hardness of the scraper of the first processing head assembly is greater than the hardness of the scraper of the second processing head assembly.

[0015] As a preferred example, the scraper of the first processing head assembly is a steel scraper, and the scraper of the second processing head assembly is a rubber strip scraper.

[0016] As a preferred example, the force applied by the scraper of the first processing head assembly to the screen during the first slurry deposition is smaller than the force applied by the scraper of the second processing head assembly to the screen during the second slurry deposition.

[0017] As a preferred example, in the first slurry deposition, the angle between the scraper of the first processing head assembly and the screen is 30 to 90 degrees; in the second slurry deposition, the angle between the scraper of the second processing head assembly and the screen is 30 to 90 degrees.

[0018] As a preferred example, the controlling the printing device to move on the screen includes: controlling the printing device to move from a first side of the screen to a second side opposite to the first side, completing a first slurry deposition, and forming a first deposited slurry on the upper surface of the substrate to be printed; controlling the printing device to move from the second side of the screen to the first side, and coating the slurry on the screen; controlling the printing device to move from the first side of the screen to the second side, completing a second slurry deposition, and forming a second deposited slurry on the upper surface of the substrate to be printed, and the second deposited slurry is at least partially stacked on the first deposited slurry.

[0019] As a preferred example, the printing device includes a first processing head assembly provided with an ink knife and a second processing head assembly provided with a scraper; during the coating slurry, the ink knife of the first processing head assembly is lowered, the scraper of the second processing head assembly does not contact the surface of the screen, and the coating slurry is completed using the ink knife of the first processing head assembly; during the first slurry deposition and the second slurry deposition, the scraper of the second processing head assembly is lowered and contacts the surface of the screen; the ink knife of the first processing head assembly is raised and does not contact the surface of the screen; and the slurry deposition is completed using the scraper of the second processing head assembly.

[0020] As a preferred example, the controlling the printing device to move on the screen includes: controlling the printing device to move from a first side of the screen to a second side opposite to the first side to complete a first slurry deposition and a second slurry deposition; in the first slurry deposition, a first deposited slurry is formed on the upper surface of the substrate to be printed; in the second slurry deposition, a second deposited slurry is formed on the upper surface of the substrate to be printed, and the second deposited slurry is at least partially stacked on the first deposited slurry.

[0021] As a preferred example, the printing device includes a first processing head assembly, a second processing head assembly, a third processing head assembly and a fourth processing head assembly, each of which has a scraper; the printing device is controlled to move from the first side of the screen to the second side opposite to the first side to complete the first slurry deposition and the second slurry deposition, including: lowering the scraper of the first processing head assembly and the scraper of the third processing head assembly to contact the screen surface; the scraper of the second processing head assembly and the scraper of the fourth processing head assembly do not contact the screen surface; controlling the printing device to move from the first side of the screen to the second side opposite to the first side, using the scraper of the third processing head assembly to complete the first slurry deposition, and using the scraper of the first processing head assembly to complete the second slurry deposition.

[0022] As a preferred example, the first processing head assembly, the second processing head assembly, the third processing head assembly and the fourth processing head assembly are arranged in sequence along the moving direction of the printing device.

[0023] As a preferred example, the amount of slurry deposited on the substrate to be printed by the scraper of the third processing head assembly is less than the amount of slurry deposited on the substrate to be printed by the scraper of the first processing head assembly.

[0024] As a preferred example, the force applied by the scraper of the third processing head assembly to the screen during the first slurry deposition is smaller than the force applied by the scraper of the first processing head assembly to the screen during the second slurry deposition.

[0025] As a preferred example, the method further includes: after printing is completed, replacing another substrate to be printed; controlling the printing device to move from the second side to the first side of the screen to complete the first slurry deposition and the second slurry deposition on the other substrate to be printed.

[0026] As a preferred example, the printing device is controlled to move from the second side to the first side of the screen to complete the first slurry deposition and the second slurry deposition on another substrate to be printed, including: lifting the scraper of the first processing head assembly and the scraper of the third processing head assembly so that they are not in contact with the screen surface; lowering the scraper of the second processing head assembly and the scraper of the fourth processing head assembly so that they are in contact with the screen surface; controlling the printing device to move from the second side to the first side of the screen, using the scraper of the second processing head assembly to complete the first slurry deposition, and using the scraper of the fourth processing head assembly to complete the second slurry deposition.

[0027] As a preferred example, the amount of slurry deposited on the substrate to be printed by the scraper of the second processing head assembly is less than the amount of slurry deposited on the substrate to be printed by the scraper of the fourth processing head assembly.

[0028] As a preferred example, the scraper of the first processing head assembly and the scraper of the fourth processing head assembly are made of a first material, and the scraper of the second processing head assembly and the scraper of the third processing head assembly are made of a second material.

[0029] As a preferred example, the hardness of the second material is greater than that of the first material.

[0030] As a preferred example, the scraper of the first processing head assembly and the scraper of the fourth processing head assembly are both rubber strip scrapers; the scraper of the second processing head assembly and the scraper of the third processing head assembly are both steel scrapers.

[0031] As a preferred example, the force applied by the scraper of the second processing head assembly to the screen during the first slurry deposition is smaller than the force applied by the scraper of the fourth processing head assembly to the screen during the second slurry deposition.

[0032] As a preferred example, in the first slurry deposition, the angle between the scraper of the third processing head assembly and the screen is 30 to 90 degrees; the angle between the scraper of the second processing head assembly and the screen is 30 to 90 degrees; in the second slurry deposition, the angle between the scraper of the first processing head assembly and the screen is 30 to 90 degrees; the angle between the scraper of the fourth processing head assembly and the screen is 30 to 90 degrees.

[0033] As a preferred example, the printing device includes a first processing head assembly and a second processing head assembly, each with a scraper; the printing device is controlled to move from the first side of the screen to the second side opposite to the first side to complete the first slurry deposition and the second slurry deposition, including: lowering the scraper of the first processing head assembly and the scraper of the second processing head assembly to contact the surface of the screen; the slurry is located on the screen, and the slurry is respectively arranged corresponding to the scraper of the first processing head assembly and the scraper of the second processing head assembly, and the slurry is respectively located in front of the moving direction of the scraper of the first processing head assembly and the scraper of the second processing head assembly; the printing device is controlled to move from the first side of the screen to the second side opposite to the first side, using the scraper of the second processing head assembly to complete the first slurry deposition, and using the scraper of the first processing head assembly to complete the second slurry deposition.

[0034] As a preferred example, the method further includes: after printing is completed, replacing another substrate to be printed; the screen is located above the other substrate to be printed; adjusting the printing device so that the slurry is located in front of the scraper of the first processing head assembly and the scraper of the second processing head assembly in the direction to be moved, respectively; controlling the printing device to move from the second side of the screen to the first side to complete the first slurry deposition and the second slurry deposition on the other substrate to be printed.

[0035] As a preferred example, the control of the printing device to move on the screen includes: controlling the printing device to move from a first side of the screen to a second side opposite to the first side, to achieve a first slurry deposition and a first slurry coating; controlling the printing device to move from the second side of the screen to the first side, to achieve a second slurry deposition and a second slurry coating; in the second slurry deposition, forming a second deposited slurry on the upper surface of the substrate to be printed, and the second deposited slurry is at least partially stacked on the first deposited slurry.

[0036] As a preferred example, the printing device includes a first processing head assembly with an ink knife, a second processing head assembly with a scraper, a third processing head assembly with a scraper, and a fourth processing head assembly with an ink knife; the first slurry deposition and the first slurry coating include: lowering the ink knife of the first processing head assembly and the scraper of the third processing head assembly so that the scraper of the third processing head assembly contacts the surface of the screen; the scraper of the second processing head assembly and the ink knife of the fourth processing head assembly do not contact the surface of the screen; controlling the printing device to move from the first side to the second side of the screen; using the scraper of the third processing head assembly to realize slurry deposition, and forming the first deposited slurry on the upper surface of the substrate to be printed; and using the ink knife of the first processing head assembly to realize the first slurry coating on the screen.

[0037] As a preferred example, the second slurry deposition and the second slurry coating include: lowering the scraper of the second processing head assembly and the ink knife of the fourth processing head assembly, so that the scraper of the second processing head assembly contacts the surface of the screen; raising the ink knife of the first processing head assembly and the scraper of the third processing head assembly, neither of which contacts the surface of the screen; controlling the printing device to move from the second side of the screen to the first side, using the scraper of the second processing head assembly to deposit the slurry, forming a second deposited slurry on the upper surface of the substrate to be printed, and the second deposited slurry is at least partially stacked on the first deposited slurry; using the ink knife of the fourth processing head assembly to coat the slurry on the screen for the second time.

[0038] As a preferred example, the printing device includes a first processing head assembly with a scraper, a second processing head assembly with an ink knife, a third processing head assembly with a scraper, and a fourth processing head assembly with an ink knife.

[0039] As a preferred example, the first processing head assembly, the second processing head assembly, the third processing head assembly and the fourth processing head assembly are arranged in sequence along the moving direction of the printing device.

[0040] As a preferred example, the printing device is controlled to move from the first side to the second side of the screen to complete the first slurry deposition and the second slurry deposition on the substrate to be printed, including: lowering the scraper of the first processing head assembly and the scraper of the third processing head assembly to contact the surface of the screen; controlling the printing device to move from the first side to the second side of the screen, using the scraper of the third processing head assembly to complete the first slurry deposition, and using the scraper of the first processing head assembly to complete the second slurry deposition, the second deposited slurry is at least partially stacked on the first deposited slurry.

[0041] As a preferred example, after completing the first slurry deposition and the second slurry deposition, it also includes: raising the scraper of the first processing head assembly and the scraper of the third processing head assembly without contacting the surface of the screen, and lowering the ink knife of the second processing head assembly and the ink knife of the fourth processing head assembly; controlling the printing device to move from the second side of the screen to the first side, and using the ink knife of the second processing head assembly and the ink knife of the fourth processing head assembly to complete the slurry coating.

[0042] As a preferred example, there is no heat treatment process between the two slurry deposition processes.

[0043] In a second aspect, the present invention provides a printing device, which adopts the aforementioned method of screen printing on a substrate.

[0044] In a third aspect, the present invention provides a solar cell, which is prepared by the aforementioned method of screen printing on a substrate.

[0045] In a fourth aspect, the present invention provides a solar cell assembly, which is prepared by using a plurality of the aforementioned solar cells.

[0046] Compared to the prior art, the method of the present invention can improve operating efficiency and achieve good printing results. The method of this embodiment includes: transferring the substrate to be printed to a printing station; moving the screen to a predetermined printing position, with the screen positioned above the substrate to be printed and the slurry positioned on the screen; controlling the movement of the printing device on the screen to deposit the slurry at least twice on the same surface of the substrate to be printed to complete printing. By achieving at least two slurry depositions at the same station, operating efficiency is improved, and the resulting grid lines have a high aspect ratio, reaching above 0.5. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIG1 is a schematic first process diagram of a first preferred embodiment of the present invention;

[0048] FIG2 is a schematic diagram of the second process of the first preferred embodiment of the present invention;

[0049] FIG3 is a schematic diagram of the first process of the second preferred embodiment of the present invention;

[0050] FIG4 is a schematic second process diagram of the second preferred embodiment of the present invention;

[0051] FIG5 is a schematic diagram of the third process of the second preferred embodiment of the present invention;

[0052] FIG6 is a schematic diagram of the first process of the third preferred embodiment of the present invention;

[0053] FIG7 is a schematic diagram of the second process of the third preferred embodiment of the present invention;

[0054] FIG8 is a schematic diagram of the first process of the fourth preferred embodiment of the present invention;

[0055] FIG9 is a schematic diagram of the second process of the fourth preferred embodiment of the present invention;

[0056] FIG10 is a schematic diagram of the first process of the fifth preferred embodiment of the present invention;

[0057] FIG11 is a schematic diagram of the second process of the fifth preferred embodiment of the present invention;

[0058] FIG12 is a schematic diagram of the first process of the sixth preferred embodiment of the present invention;

[0059] FIG13 is a schematic diagram of the second process of the sixth preferred embodiment of the present invention;

[0060] 14 is a schematic structural diagram of the printing unit of the present invention;

[0061] FIG15 is a schematic structural diagram of the printing device of the present invention. DETAILED DESCRIPTION

[0062] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0063] The application has a wide range of applications, wherein as an example, the substrate is a silicon-based solar cell formed with a transparent conductive layer, and printing is performed on the substrate to be printed to form a grid line electrode on the transparent conductive layer.

[0064] An embodiment of the present invention provides a method for screen printing on a substrate, comprising:

[0065] Step 10: The substrate to be printed is transported to the printing station. For example, the substrate to be printed is transported to the printing station by a conveyor belt, a rotary table, or other conveying means. Printing is performed on the substrate to be printed at the printing station.

[0066] Step 20: Move the screen to a predetermined printing position, with the screen positioned above the substrate to be printed and the slurry positioned on the screen. After the substrate to be printed is transferred to the printing station, move the screen to a predetermined printing position, with the screen positioned above the substrate to be printed.

[0067] Step 30: Control the printing device to move on the screen, deposit the slurry at least twice on the same substrate to be printed, and complete the printing process. During the printing process, the slurry is pushed and displaced by the printing device, so that the slurry is deposited on the substrate to be printed through the screen.

[0068] Compared to the prior art, which completes printing with a single slurry deposition on the substrate to be printed, this embodiment completes printing by depositing the slurry at least twice on the upper surface of the same substrate to be printed. As shown in Figure 14, the printing portion formed on the upper surface of the same substrate to be printed includes a first slurry deposition 20 located below and a second slurry deposition 19 located above. At the same station, by increasing the number of slurry depositions, the aspect ratio of the printed grid lines can reach over 25%. At the same time, compared to existing multi-station printing, the method of this embodiment completes multiple slurry depositions at the same station, significantly improving work efficiency.

[0069] In the prior art, after the first printing process using a screen on a transparent conductive film layer, the first deposited slurry requires heat treatment, such as baking, before proceeding to the second printing station. In the second printing station, a second printing process using a screen is performed on the transparent conductive film layer, forming a second deposited slurry. In the above embodiment, no heat treatment is performed between the two slurry deposition processes. This method eliminates the existing slurry drying and heat treatment process, simplifying the process and improving efficiency.

[0070] As a preferred example, printing is accomplished by depositing the slurry twice on the upper surface of the same substrate to be printed. This double slurry deposition process allows for grid lines with a higher aspect ratio. While maintaining the desired printing quality, reducing the number of slurry depositions improves efficiency, simplifies the structure of the printing equipment, and reduces manufacturing costs.

[0071] The printing device described in this embodiment, as shown in Figure 15, includes a processing head assembly, a lifting device 23, a base 21, and a horizontal moving device 22. The processing head assembly is connected to the lifting device 23, which is connected to the base 21, which is connected to the horizontal moving device 22. The processing head assemblies have the same primary structure. For example, the first, second, third, and fourth processing head assemblies described herein have the same primary structure. The processing head assembly includes a bracket and a cutting tool connected to the bottom end of the bracket. The lifting device drives the processing head assembly up and down, while the horizontal moving device 22 drives the processing head assembly horizontally, for example, left and right. Preferably, the horizontal moving device 22 drives all processing head assemblies to move synchronously within the horizontal plane. The cutting tool can be a scraper or an ink knife. Multiple processing head assemblies can be installed in the same printing device. As shown in Figure 15, the printing device is equipped with two processing head assemblies. The choice of scraper or ink knife is determined based on actual conditions. The same printing device can drive all cutting tools for synchronous horizontal movement, and the lifting and lowering of individual processing head assemblies can also be adjusted individually.

[0072] In a first preferred embodiment, as shown in Figure 1, the printing device comprises a first processing head assembly provided with a scraper 5 and a second processing head assembly provided with a scraper 6. The first processing head assembly and the second processing head assembly are arranged along the moving direction of the printing device.

[0073] In step 30, controlling the printing device to move on the screen includes:

[0074] In step 3011 , the printing device is controlled to move from a first side of the screen plate 2 to a second side opposite to the first side, to complete the first slurry deposition, and to form the first deposited slurry on the upper surface of the substrate to be printed.

[0075] The first side and the second side are two opposing sides of the stencil. As indicated by the arrow in Figure 1, movement occurs from the first side of the stencil toward the second side. As indicated by the arrow in Figure 2, movement occurs from the second side of the stencil toward the first side. During the first slurry deposition, the scraper of the first processing head assembly is lowered into contact with the stencil surface, while the scraper of the second processing head assembly does not. The first slurry deposition is completed using the scraper of the first processing head assembly. As shown in Figure 1, during the first slurry deposition, only the scraper 5 of the first processing head assembly contacts the stencil 2. The slurry 4 moves across the surface of the stencil 2 as the scraper 5 of the first processing head assembly moves. During this movement, a portion of the slurry 4 is deposited onto the upper surface of the substrate 1 to be printed, forming the first deposited slurry. During the first slurry deposition, the scraper 6 of the second processing head assembly does not contact the surface of the stencil 2 and does not apply any force to the slurry.

[0076] In step 3012, the printing device is controlled to move from the second side toward the first side of the screen to complete the second slurry deposition, forming a second deposited slurry on the upper surface of the substrate to be printed, and the second deposited slurry is at least partially stacked on the first deposited slurry.

[0077] During the second slurry deposition, as shown in Figure 2, the scraper 6 of the second processing head assembly is lowered into contact with the surface of the stencil 2. The scraper 5 of the first processing head assembly is raised, no longer in contact with the surface of the stencil 2. The second slurry deposition is completed using the scraper 6 of the second processing head assembly. During the second slurry deposition, the scraper 6 of the second processing head assembly contacts the surface of the stencil 2. The scraper 6 of the second processing head assembly moves the slurry 4 across the surface of the stencil 2. During this movement, a portion of the slurry is deposited onto the substrate 1 to be printed, forming a second deposit of slurry. The second deposited slurry is at least partially stacked on the first deposited slurry.

[0078] In this embodiment, the first slurry deposition serves as the substrate. The second slurry deposition and the first slurry deposition collectively form the printing section. In this embodiment, the printing device reciprocates once between the first and second sides of the stencil, for a total of two movements, thereby depositing slurry twice on the same substrate to be printed.

[0079] In this embodiment, the amount of slurry deposited on the substrate to be printed in the first slurry deposition is equal to or greater than the amount of slurry deposited on the substrate to be printed in the second slurry deposition. However, preferably, the amount of slurry deposited on the substrate to be printed in the first slurry deposition is less than the amount of slurry deposited on the substrate to be printed in the second slurry deposition. The amount of slurry in the first slurry deposition is relatively small, acting as a substrate. The amount of slurry in the second slurry deposition is relatively large, which can fill the mesh of the screen plate, thereby achieving the purpose of having a higher aspect ratio of the grid lines after printing. At the same time, the grid lines formed by printing have a more stable structure and are not easy to break.

[0080] In this embodiment, the hardness of the scraper of the first processing head assembly is less than or equal to the hardness of the scraper of the second processing head assembly. However, preferably, the hardness of the scraper of the first processing head assembly is greater than the hardness of the scraper of the second processing head assembly. In this way, the contact area between the scraper of the first processing head assembly and the mesh is smaller than the contact area between the scraper of the second processing head assembly and the mesh, so that the scraper of the second processing head assembly can scrape more slurry. Preferably, the scraper of the first processing head assembly is a steel scraper, and the scraper of the second processing head assembly is a rubber strip scraper. Steel scrapers and rubber strip scrapers are only preferred options, and those skilled in the art can also use scrapers made of other materials.

[0081] In this embodiment, the force applied by the scraper of the first processing head assembly to the stencil during the first slurry deposition is equal to or greater than the force applied by the scraper of the second processing head assembly to the stencil during the second slurry deposition. However, preferably, the force applied by the scraper of the first processing head assembly to the stencil during the first slurry deposition is less than the force applied by the scraper of the second processing head assembly to the stencil during the second slurry deposition. In this way, the amount of slurry deposited in the first slurry deposition is less, while the amount of slurry deposited in the second slurry deposition is more. The printed grid lines have a more stable structure and are less prone to breakage.

[0082] In this embodiment, preferably, in the first slurry deposition, the angle between the scraper of the first processing head assembly and the screen is 30 to 90 degrees; in the second slurry deposition, the angle between the scraper of the second processing head assembly and the screen is 30 to 90 degrees.

[0083] In a second preferred embodiment, the printing device comprises a first processing head assembly provided with an ink knife and a second processing head assembly provided with a scraper. The first processing head assembly and the second processing head assembly are arranged along a moving direction of the printing device.

[0084] In step 30, controlling the printing device to move on the screen specifically includes:

[0085] Step 3021 controls the printing device to move from a first side of the stencil to a second side opposite the first side, completing the first slurry deposition and forming the first deposited slurry on the upper surface of the substrate to be printed. As shown in Figure 3, the printing device moves from the left side of the illustrated stencil to the right side. The scraper 8 of the second processing head assembly is lowered to contact the surface of the stencil 2; the ink knife 7 of the first processing head assembly is raised to not contact the surface of the stencil 2. The scraper 8 of the second processing head assembly acts on the slurry already coated on the stencil, causing some of the slurry to separate from the stencil and fall onto the substrate to be printed below the stencil, forming the first deposited slurry.

[0086] Step 3022 controls the printing device to move from the second side of the stencil toward the first side, coating the stencil with slurry. As shown in Figure 4, the printing device moves from the right side of the stencil to the left side. The ink blade 7 of the first processing head assembly is lowered, not in contact with the surface of the stencil 2; the scraper 8 of the second processing head assembly is raised, not in contact with the surface of the stencil 2. The ink blade 7 drives the slurry 4 in front of it to move across the surface of the stencil 2. The slurry 4 is again coated on the surface of the stencil 2 using the ink blade 7 of the first processing head assembly, completing the slurry coating.

[0087] Step 3023 controls the printing device to move from the first side to the second side of the screen to complete the second slurry deposition, forming a second deposited slurry on the upper surface of the substrate to be printed, and the second deposited slurry is at least partially stacked on the first deposited slurry. As shown in Figure 5, the printing device moves from the left side to the right side of the screen. The scraper 8 of the second processing head assembly is lowered to contact the surface of the screen 2; the ink knife 7 of the first processing head assembly is raised and does not contact the surface of the screen 2. The scraper 8 of the second processing head assembly acts on the slurry that has been coated on the screen, causing part of the slurry to separate from the screen and fall onto the substrate to be printed below the screen, forming a second deposited slurry, and the second deposited slurry is at least partially stacked on the first deposited slurry.

[0088] Before step 3021 , the method may further include: controlling the printing device to move from the second side toward the first side of the screen to coat the slurry on the screen.

[0089] In the second preferred embodiment, an ink blade and a scraper are used in conjunction. Before the scraper is used, the ink blade is used to coat the stencil with slurry. This ensures that sufficient slurry is present on the stencil during the scraper operation. In this second preferred embodiment, the printing device must reciprocate four times on both sides to form the first and second deposits of slurry on the substrate to be printed, completing the printing process.

[0090] It should be noted that, in this solution, slurry deposition may be performed three or more times, which will not be further explained here.

[0091] In a third preferred embodiment, the printing device includes a first processing head assembly with a scraper, a second processing head assembly with a scraper, a third processing head assembly with a scraper, and a fourth processing head assembly with a scraper. The first processing head assembly, the second processing head assembly, the third processing head assembly, and the fourth processing head assembly are arranged in sequence along the direction of movement of the printing device.

[0092] In step 30, controlling the printing device to move on the screen specifically includes:

[0093] Step 3031 controls the printing device to move from a first side of the screen toward a second side opposite to the first side, completing a first slurry deposition and a second slurry deposition; in the first slurry deposition, a first deposited slurry is formed on the upper surface of the substrate to be printed; in the second slurry deposition, a second deposited slurry is formed on the upper surface of the substrate to be printed, and the second deposited slurry is at least partially stacked on the first deposited slurry. The first and second slurry depositions include:

[0094] As shown in FIG6 , step 30311 involves lowering the scraper 9 of the first processing head assembly and the scraper 11 of the third processing head assembly to contact the surface of the stencil 2. The scraper 10 of the second processing head assembly and the scraper 12 of the fourth processing head assembly are no longer in contact with the surface of the stencil 2. In the direction of movement, slurry 4 is positioned in front of the scraper 9 of the first processing head assembly and the scraper 11 of the third processing head assembly, respectively.

[0095] As shown in Figure 6, step 30312 controls the printing device to move from a first side of the stencil to a second side opposite the first side, that is, from the left side to the right side in the diagram. The printing device is sequentially provided with a first processing head assembly with a scraper 9, a second processing head assembly with a scraper 10, a third processing head assembly with a scraper 11, and a fourth processing head assembly with a scraper 12 along the direction of movement. The scraper 11 of the third processing head assembly completes the first slurry deposition, while the scraper 9 of the first processing head assembly completes the second slurry deposition. The scraper 11 of the third processing head assembly operates before the scraper 9 of the first processing head assembly. The scraper 11 of the third processing head assembly moves the slurry across the surface of the stencil 2. During this movement, the slurry 4 is partially deposited onto the substrate 1 to be printed, forming the first deposited slurry. The scraper 9 of the first processing head assembly moves the slurry 4 across the surface of the stencil 2. During this movement, the slurry is partially deposited onto the substrate 1 to be printed, forming the second deposited slurry. The second deposited slurry is at least partially stacked on the first deposited slurry.

[0096] In the above method, the printing device moves from a first side of the stencil to a second side opposite the first side, completing both the first and second slurry depositions. During this process, the printing device moves from one side of the stencil to the other, completing two slurry depositions. While also completing slurry deposition on both sides, the printing device travels half the path of the first preferred example and one-quarter the path of the second preferred example. The shorter travel path of the printing device in this preferred example significantly improves work efficiency.

[0097] In step 30312, the amount of slurry deposited onto the substrate to be printed by the scraper of the third processing head assembly is greater than or equal to the amount of slurry deposited onto the substrate to be printed by the scraper of the first processing head assembly. Preferably, the amount of slurry deposited onto the substrate to be printed by the scraper of the third processing head assembly is less than the amount of slurry deposited onto the substrate to be printed by the scraper of the first processing head assembly. The amount of slurry in the first slurry deposition is relatively small, acting as a substrate. The amount of slurry in the second slurry deposition is relatively large, which can fill the mesh of the screen, thereby achieving the purpose of having a higher aspect ratio of the printed grid lines.

[0098] In this embodiment, the force applied by the scraper of the third processing head assembly to the stencil during the first slurry deposition is greater than or equal to the force applied by the scraper of the first processing head assembly to the stencil during the second slurry deposition. However, preferably, the force applied by the scraper of the third processing head assembly to the stencil during the first slurry deposition is less than the force applied by the scraper of the first processing head assembly to the stencil during the second slurry deposition. In this way, the amount of slurry in the first slurry deposition is less, while the amount of slurry in the second slurry deposition is more. The printed grid lines have a more stable structure and are less prone to breakage.

[0099] In the third preferred embodiment, step 3032 is performed after step 3031. Step 3032 includes:

[0100] After step 30321 printing is completed, another substrate to be printed is replaced.

[0101] As shown in FIG. 7 , step 30322 controls the printing device to move from the second side toward the first side of the screen to complete the first slurry deposition and the second slurry deposition on another substrate to be printed.

[0102] In step 3031, the printing device moves from the first side of the stencil to the second side, completing printing on the substrate to be printed. Then, in step 3032, the printing device moves from its rest position, i.e., the second side of the stencil, back to the first side of the stencil, completing printing on another substrate to be printed. Step 3032 continues the movement of the printing device in step 3031, and during this movement, two slurry depositions are performed on the other substrate to be printed. This significantly improves the operating efficiency of the printing device.

[0103] In a first preferred embodiment, the printing device reciprocates once to complete printing on one substrate to be printed. In a second preferred embodiment, the printing device reciprocates twice to complete printing on one substrate to be printed. In a third preferred embodiment, the printing device reciprocates once to complete printing on two substrates to be printed.

[0104] Furthermore, the printing device is provided with a first processing head assembly with a scraper 9, a second processing head assembly with a scraper 10, a third processing head assembly with a scraper 11, and a fourth processing head assembly with a scraper 12, sequentially along the direction of movement. After the first and second slurry depositions on the substrate to be printed are completed, the slurry is located on the side of the scraper 9 of the first processing head assembly and the scraper 11 of the third processing head assembly, respectively, near the second side of the stencil. Therefore, before printing another substrate to be printed, the scrapers 9 and 11 of the first processing head assembly can be raised, while the scrapers 10 and 12 of the second processing head assembly can be lowered. At this point, the slurry is located on the side of the scraper 10 and scraper 12 of the fourth processing head assembly, respectively, in the direction of movement. As shown in FIG. 7 , this arrangement simplifies the process and improves printing efficiency.

[0105] Specifically, in step 30322, the printing device is controlled to move from the second side toward the first side of the screen to complete the first slurry deposition and the second slurry deposition on another substrate to be printed, as shown in FIG7 , including:

[0106] In step 303221, the scraper 9 of the first processing head assembly and the scraper 11 of the third processing head assembly are lifted so as not to contact the surface of the screen 2; the scraper 10 of the second processing head assembly and the scraper 12 of the fourth processing head assembly are lowered so as to contact the surface of the screen 2.

[0107] In step 303222, the printing device is controlled to move from the second side to the first side of the screen, and the scraper 10 of the second processing head assembly is used to complete the first slurry deposition, and the scraper 12 of the fourth processing head assembly is used to complete the second slurry deposition.

[0108] The scraper 10 of the second processing head assembly operates before the scraper 12 of the fourth processing head assembly. The scraper 10 of the second processing head assembly moves the slurry across the stencil surface. During this movement, some of the slurry is deposited onto the substrate to be printed, forming a first deposit of slurry. The scraper 12 of the fourth processing head assembly moves the slurry across the stencil surface. During this movement, some of the slurry is deposited onto the substrate to be printed, forming a second deposit of slurry. The second deposit of slurry is at least partially stacked on the first deposit of slurry.

[0109] In the above method, the printing device moves from the second side to the first side of the screen to complete the first slurry deposition and the second slurry deposition on another substrate to be printed.

[0110] In step 303222, the amount of slurry deposited onto the substrate to be printed by the scraper of the second processing head assembly is greater than or equal to the amount of slurry deposited onto the substrate to be printed by the scraper of the fourth processing head assembly. Preferably, the amount of slurry deposited onto the substrate to be printed by the scraper of the second processing head assembly is less than the amount of slurry deposited onto the substrate to be printed by the scraper of the fourth processing head assembly. The amount of slurry in the first slurry deposition is relatively small, acting as a substrate. The amount of slurry in the second slurry deposition is relatively large, which can fill the mesh of the screen, thereby achieving the purpose of having a higher aspect ratio of the printed grid lines.

[0111] In a third preferred embodiment, the scraper of the first processing head assembly and the scraper of the fourth processing head assembly are made of a first material, and the scraper of the second processing head assembly and the scraper of the third processing head assembly are made of a second material. The material of the first material and the second material can be the same. However, preferably, the material of the first material and the second material is different. Preferably, the hardness of the second material is greater than the hardness of the first material. In this way, the contact area between the scraper of the first processing head assembly and the mesh is greater than the contact area between the scraper of the third processing head assembly and the mesh, so that the scraper of the first processing head assembly can scrape more slurry. For example, the scraper of the first processing head assembly and the scraper of the fourth processing head assembly are both rubber strip scrapers; the scraper of the second processing head assembly and the scraper of the third processing head assembly are both steel scrapers.

[0112] In step 303222, the force applied by the scraper of the second processing head assembly to the screen during the first slurry deposition is greater than or equal to the force applied by the scraper of the fourth processing head assembly to the screen during the second printing. However, preferably, the force applied by the scraper of the second processing head assembly to the screen during the first slurry deposition is less than the force applied by the scraper of the fourth processing head assembly to the screen during the second slurry deposition. The amount of slurry in the first slurry deposition is relatively small, and it acts as a substrate. The amount of slurry in the second slurry deposition is relatively large, and it can fill the mesh of the screen, so that the grid lines after printing have a higher aspect ratio. At the same time, the grid lines formed by printing have a more stable structure and are not easy to break.

[0113] Preferably, in the first printing, the angle between the scraper of the first processing head assembly and the screen is 30 to 90 degrees; the angle between the scraper of the third processing head assembly and the screen is 30 to 90 degrees; in the second printing, the angle between the scraper of the second processing head assembly and the screen is 30 to 90 degrees; the angle between the scraper of the fourth processing head assembly and the screen is 30 to 90 degrees.

[0114] A fourth preferred embodiment controls the printing device to move on the screen, including: controlling the printing device to move from a first side of the screen to a second side opposite to the first side, to complete a first slurry deposition and a second slurry deposition; in the first slurry deposition, a first deposited slurry is formed on the upper surface of the substrate to be printed; in the second slurry deposition, a second deposited slurry is formed on the upper surface of the substrate to be printed, and the second deposited slurry is at least partially stacked on the first deposited slurry.

[0115] In a fourth preferred embodiment, the printing device includes a first processing head assembly with a scraper 17 and a second processing head assembly with a scraper 18. The first processing head assembly and the second processing head assembly are arranged along the movement direction of the printing device. The printing device is controlled to move from a first side of the screen to a second side opposite to the first side to complete the first slurry deposition and the second slurry deposition, as shown in FIG8 , including:

[0116] In step 3041, the scraper 17 of the first processing head assembly and the scraper 18 of the second processing head assembly are lowered to contact the surface of the stencil 2. The slurry 4 is located on the stencil 2. The slurry 4 is respectively arranged corresponding to the scraper 17 of the first processing head assembly and the scraper 18 of the second processing head assembly, and the slurry 4 is respectively located in front of the scraper 17 of the first processing head assembly and the scraper 18 of the second processing head assembly in the moving direction.

[0117] In step 3042 , the printing device is controlled to move from the first side of the screen 2 to the second side opposite to the first side, and the first slurry deposition is completed using the scraper 18 of the second processing head assembly, and the second slurry deposition is completed using the scraper 17 of the first processing head assembly.

[0118] In the fourth preferred embodiment, the printing device moves once to complete two slurry depositions on the same substrate to be printed.

[0119] After printing is completed, the method further comprises:

[0120] After step 3043 printing is completed, another substrate to be printed is replaced;

[0121] In step 3044, the stencil is positioned above another substrate to be printed. The printing mechanism is adjusted so that the slurry 4 is located in front of the direction of movement of the scraper 17 of the first processing head assembly and the scraper 18 of the second processing head assembly. As shown in Figure 9, the printing mechanism moves from the right side of the stencil to the left side of the stencil. At the starting position (i.e., the right side of the stencil), there is a slurry 4 to the left of the scraper 17 of the first processing head assembly and to the left of the scraper 18 of the second processing head assembly.

[0122] In step 3045 , the printing device is controlled to move from the second side toward the first side of the screen to complete the first slurry deposition and the second slurry deposition on another substrate to be printed.

[0123] Similar to the third preferred example, the printing device of the fourth preferred example can also complete two slurry depositions and complete the printing work in one stroke. In the third preferred example, when the printing device changes the moving direction, there is no need to adjust the horizontal position of the processing head assembly, and it is only necessary to raise and lower the processing head assembly. However, in the fourth preferred example, when the printing device changes the moving direction, it is necessary to first adjust the position of the processing head assembly in the horizontal direction so that the slurry is located in front of the scraper after the moving direction is changed. In this way, the scraper can drive the slurry to move on the screen. After adjusting the position of the processing head assembly in the horizontal direction, the processing head assembly is lowered to make the scraper contact with the screen. Compared with the fourth preferred example, the adjustment of the processing head assembly in the third preferred example is simpler and more reliable.

[0124] In a fifth preferred embodiment, as shown in FIG10 , the printing device includes a first processing head assembly with an ink cutter 13, a second processing head assembly with a scraper 14, a third processing head assembly with a scraper 15, and a fourth processing head assembly with an ink cutter 16. The first processing head assembly, the second processing head assembly, the third processing head assembly, and the fourth processing head assembly are arranged in sequence along the moving direction of the printing device.

[0125] In step 30, controlling the printing device to move on the screen specifically includes:

[0126] Step 3051 controls the printing device to move from a first side of the screen toward a second side opposite to the first side, to achieve a first slurry deposition and a first slurry coating.

[0127] Step 3052 controls the printing device to move from the second side of the screen toward the first side to achieve a second slurry deposition and a second overcoating slurry; in the second slurry deposition, a second deposition slurry is formed on the upper surface of the substrate to be printed, and the second deposition slurry is at least partially stacked on the first deposition slurry.

[0128] In step 3051, a first slurry deposition and a first overcoat of slurry are performed, including: as shown in FIG10 , lowering the ink blade 13 of the first processing head assembly and the scraper 15 of the third processing head assembly so that the scraper 15 of the third processing head assembly contacts the surface of the stencil 2, while the ink blade 13 of the first processing head assembly does not; controlling the scraper 14 of the second processing head assembly and the ink blade 16 of the fourth processing head assembly to not contact the surface of the stencil 2; and controlling the printing device to move from a first side toward a second side of the stencil 2, with the ink blade 13 of the first processing head assembly positioned upstream of the scraper 15 of the third processing head assembly. Slurry is deposited using the scraper 15 of the third processing head assembly, forming a first deposit of slurry on the upper surface of the substrate 1 to be printed. During this process, the distance between the ink blade 13 of the first processing head assembly and the stencil 2 is less than the distance between the ink blade 16 of the fourth processing head assembly and the stencil 2. The ink blade 13 of the first processing head assembly is used to apply the first overcoat of slurry to the stencil 2.

[0129] In this embodiment, the scraper 15 operates before the ink blade 13. The scraper 15 deposits the slurry. After the scraper 15 forms the first deposit of slurry on the surface of the substrate 1 to be printed, the ink blade 13 applies the slurry between the scraper 15 and the ink blade 13 to the screen, preparing for the next scraping of slurry.

[0130] Before step 3051, the method further includes controlling the printing device to move on the stencil to coat the stencil with slurry. At least one of the ink blades of the first processing head assembly and the ink blades of the fourth processing head assembly is lowered, without contacting the stencil surface, and moves from one side of the stencil to the other side to coat the stencil with slurry.

[0131] In step 3052, the second slurry deposition and the second slurry coating are achieved, including: as shown in Figure 11, lowering the scraper 14 of the second processing head assembly and the ink knife 16 of the fourth processing head assembly, so that the scraper 14 of the second processing head assembly contacts the surface of the screen 2, and the ink knife 16 of the fourth processing head assembly does not contact the surface of the screen 2; raising the ink knife 13 of the first processing head assembly and the scraper 15 of the third processing head assembly, so that neither of them contacts the surface of the screen 2; controlling the printing device to move from the second side to the first side of the screen 2, and the ink knife 16 of the fourth processing head assembly is located upstream of the scraper 14 of the second processing head assembly, and utilizing the scraper 14 of the second processing head assembly to achieve slurry deposition, forming a second deposited slurry on the upper surface of the substrate to be printed, and the second deposited slurry is at least partially stacked on the first deposited slurry. During this process, the distance between the ink knife 16 of the fourth processing head assembly and the screen 2 is smaller than the distance between the ink knife 13 of the first processing head assembly and the screen 2, and the ink knife 16 of the fourth processing head assembly is used to coat the slurry on the screen for the second time.

[0132] In the fifth preferred embodiment, step 3053 is completed, that is, two slurry depositions are completed on the same substrate to be printed, and the printing work is completed. After step 3053, the process returns to step 3052 and the process is cyclical until the printing is completed or the slurry on the screen is used up, and then the slurry is replenished.

[0133] In the fifth preferred embodiment, except for the initial slurry application, the printing device needs to make one reciprocating movement each time to complete printing on the substrate. In the second preferred embodiment, during one movement of the printing device, for example, when moving from a first side of the stencil to a second side, only one of the scraper and ink blade is in operation. In the fifth preferred embodiment, during one movement of the printing device, one scraper and one ink blade are simultaneously in operation.

[0134] The ink knife coats the slurry between the scraper performing deposition and the ink knife performing coating onto the screen, thereby preparing for the next scraping of the slurry. Compared with the second preferred embodiment, the fifth preferred embodiment improves work efficiency.

[0135] In a sixth preferred embodiment, the printing device moves once to complete two slurry depositions on the same substrate to be printed, and then the slurry is coated by an ink knife;

[0136] In the sixth preferred embodiment, as shown in FIG12 , the printing device includes a first processing head assembly with a scraper 26 , a second processing head assembly with an ink knife 24 , a third processing head assembly with a scraper 27 and a fourth processing head assembly with an ink knife 25 .

[0137] Preferably, the first processing head assembly, the second processing head assembly, the third processing head assembly and the fourth processing head assembly are arranged in sequence along the moving direction of the printing device.

[0138] In a sixth preferred embodiment, as shown in FIG12 , the controlling the printing device to move from the first side to the second side of the screen to complete the first slurry deposition and the second slurry deposition on the substrate to be printed includes:

[0139] The scraper 26 of the first processing head assembly and the scraper 27 of the third processing head assembly are lowered to contact the surface of the screen; the printing device is controlled to move from the first side to the second side of the screen, and the first slurry deposition is completed by the scraper 27 of the third processing head assembly, and the second slurry deposition is completed by the scraper 26 of the first processing head assembly, and the second deposited slurry is at least partially stacked on the first deposited slurry.

[0140] In a sixth preferred embodiment, as shown in FIG13 , after the first slurry deposition and the second slurry deposition are completed, the method further includes:

[0141] Raise the scraper 26 of the first processing head assembly and the scraper 27 of the third processing head assembly so that they do not contact the stencil surface, and lower the ink knife 24 of the second processing head assembly and the ink knife 25 of the fourth processing head assembly;

[0142] The printing device is controlled to move from the second side to the first side of the screen, and the ink knife 24 of the second processing head assembly and the ink knife 25 of the fourth processing head assembly are used to complete the coating of the slurry.

[0143] Compared with the fifth preferred embodiment, the sixth preferred embodiment can achieve two consecutive slurry depositions on the same substrate surface in one printing operation, and the printed substrate is transferred out of the printing station during the slurry coating process of the ink knife. Optionally, another substrate to be printed can be transferred, which improves work efficiency.

[0144] In the sixth preferred embodiment, preferably, the amount of slurry deposited on the substrate to be printed in the first slurry deposition is less than the amount of slurry deposited on the substrate to be printed in the second slurry deposition.

[0145] In the sixth preferred example, preferably, the hardness of the scraper of the third processing head assembly is greater than the hardness of the scraper of the first processing head assembly.

[0146] In the sixth preferred example, preferably, the scraper of the third processing head assembly is a steel scraper, and the scraper of the first processing head assembly is a rubber strip scraper.

[0147] In the sixth preferred example, preferably, the force applied by the scraper of the third processing head assembly to the screen during the first slurry deposition is smaller than the force applied by the scraper of the first processing head assembly to the screen during the second slurry deposition.

[0148] In the sixth preferred example, preferably, in the first slurry deposition, the angle between the scraper of the third processing head assembly and the screen is 30 to 90 degrees; in the second slurry deposition, the angle between the scraper of the first processing head assembly and the screen is 30 to 90 degrees.

[0149] In the various embodiments and preferred examples described above, it is possible to achieve two consecutive slurry depositions on the surface of the same substrate to be printed at the same workstation through the same screen to complete printing.

[0150] In the various embodiments and preferred examples described above, the screen can be a silk screen or a metal screen, preferably a metal screen. The embodiments or preferred examples described above enable at least two consecutive slurry depositions to be performed on the same substrate surface at the same station using the same screen to complete printing. This eliminates the need for conventional techniques, which involve drying the slurry after one printing step before a second printing step, which is a complex process and requires alignment during the second printing step, increasing the process complexity.

[0151] Compared with the prior art using silk screen printing technology, this preferred example uses metal screen printing. First, during the printing process, the deformation of the metal screen is smaller than that of the silk screen. When the second slurry deposition is performed, the metal screen alignment accuracy is higher. Secondly, the opening of the metal screen is fully open and there are no mesh knots, while the silk screen may have mesh knots at the opening. Due to the presence of mesh knots, the silk screen may further affect the uniformity after the two slurry depositions are stacked. Therefore, based on the difference in the printing principles and structures of metal screens and silk screens, it is preferred to select a metal screen as the printing screen. Specifically, the metal screen is a steel mesh. For example, the metal screen can form an opening on a metal plate by laser opening. Compared with the silk screen, the opening width of the steel screen is between 5 and 15 microns, or can be smaller. During the metal screen printing process, the slurry passes through the openings, making the first and second slurry deposition processes more uniform. Consequently, the grid lines formed by the stacked first and second deposited slurries are narrower and taller. The resulting grid lines have a higher aspect ratio after printing, improving the battery's conductive properties and thus increasing overall battery efficiency. Furthermore, the printing method of the present invention improves the printing efficiency of battery cells and increases production capacity.

[0152] This embodiment also provides a printing device, which executes the aforementioned method of screen printing on a substrate, and is used to realize printing on the substrate, thereby improving operation efficiency and enhancing printing effects.

[0153] This embodiment further provides a solar cell, which is prepared by the aforementioned method of screen printing on a substrate.

[0154] This embodiment also provides a solar cell assembly, which is formed by using a plurality of the above solar cells. When a solar cell or solar cell assembly uses the printing method of the above embodiment or preferred example to prepare grid lines, grid lines with a high aspect ratio can be obtained, thereby improving the battery conversion rate.

[0155] Using the method described in the fourth preferred embodiment, grid lines were printed on a silicon-based solar cell having a transparent conductive layer. The screen was a steel mesh. The scrapers of the first processing head assembly and the second processing head assembly were both steel scrapers. The height and width of the grid lines produced using the above method were measured at six different locations, with the data obtained as shown in Table 1.

[0156] Table 1

[0157] In Table 1, the average aspect ratio at six different locations is 0.528, which is higher than the grid line aspect ratio obtained with existing technologies. The silicon-based solar cell prepared by the above method was subjected to an ETA test, and the test showed an ETA of 26.2%.

[0158] The foregoing is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art will appreciate that the foregoing specific embodiments are merely illustrative and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art based on the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for screen printing on a substrate, comprising: Transmitting the substrate to be printed to the printing station; Moving the screen to a predetermined printing position, with the screen located above the substrate to be printed and the paste located on the screen; Controlling the printing device to move on the screen, depositing the paste on the upper surface of the same substrate to be printed at least twice to complete the printing.

2. The method according to claim 1, wherein Depositing the paste on the upper surface of the same substrate to be printed twice to complete the printing.

3. The method according to claim 1, wherein, The controlling the printing device to move on the screen includes: Controlling the printing device to move from the first side of the screen to the second side opposite the first side to complete the first paste deposition, forming the first deposited paste on the upper surface of the substrate to be printed; Controlling the printing device to move from the second side of the screen to the first side to complete the second paste deposition, forming the second deposited paste on the upper surface of the substrate to be printed, and at least part of the second deposited paste is stacked on the first deposited paste.

4. The method according to claim 3, wherein The printing device includes a first processing head assembly provided with a squeegee and a second processing head assembly provided with a squeegee; In the first paste deposition, lowering the squeegee of the first processing head assembly to contact the surface of the screen, and the squeegee of the second processing head assembly not contacting the surface of the screen, and using the squeegee of the first processing head assembly to complete the first paste deposition; In the second paste deposition, lowering the squeegee of the second processing head assembly to contact the surface of the screen; raising the squeegee of the first processing head assembly so that it does not contact the surface of the screen; and using the squeegee of the second processing head assembly to complete the second paste deposition.

5. The method according to claim 4, wherein, The amount of paste deposited on the substrate to be printed in the first paste deposition is less than the amount of paste deposited on the substrate to be printed in the second paste deposition.

6. The method according to claim 4, wherein The hardness of the squeegee of the first processing head assembly is greater than the hardness of the squeegee of the second processing head assembly.

7. The method according to claim 6, wherein, The squeegee of the first processing head assembly is a steel squeegee, and the squeegee of the second processing head assembly is a rubber strip squeegee.

8. The method according to claim 4, wherein, The force exerted by the squeegee of the first processing head assembly on the screen in the first paste deposition is less than the force exerted by the squeegee of the second processing head assembly on the screen in the second paste deposition.

9. The method according to claim 4, wherein In the first paste deposition, the angle between the squeegee of the first processing head assembly and the screen is 30 to 90 degrees; in the second paste deposition, the angle between the squeegee of the second processing head assembly and the screen is 30 to 90 degrees.

10. The method according to claim 1, wherein, The controlling the printing device to move on the screen includes: Controlling the printing device to move from the first side of the screen to the second side opposite the first side to complete the first paste deposition, forming the first deposited paste on the upper surface of the substrate to be printed; Controlling the printing device to move from the second side of the screen to the first side to apply a coating of paste on the screen; Controlling the printing device to move from the first side of the screen to the second side to complete the second paste deposition, forming the second deposited paste on the upper surface of the substrate to be printed, and at least part of the second deposited paste is stacked on the first deposited paste.

11. The method according to claim 10, wherein, The printing device includes a first processing head assembly provided with an ink knife and a second processing head assembly provided with a squeegee; In the coating of the paste, lowering the ink knife of the first processing head assembly, and the squeegee of the second processing head assembly not contacting the surface of the screen, and using the ink knife of the first processing head assembly to complete the coating of the paste; In the first paste deposition and the second paste deposition, the squeegee of the second processing head assembly is lowered to contact the surface of the stencil; the ink knife of the first processing head assembly is raised to not contact the surface of the stencil; the paste deposition is completed by using the squeegee of the second processing head assembly.

12. The method according to claim 2, wherein, The controlling the printing device to move on the stencil includes: Controlling the printing device to move from the first side of the stencil to the second side opposite to the first side to complete the first paste deposition and the second paste deposition; in the first paste deposition, a first deposited paste is formed on the upper surface of the substrate to be printed; in the second paste deposition, a second deposited paste is formed on the upper surface of the substrate to be printed, and at least a part of the second deposited paste is stacked on the first deposited paste.

13. The method according to claim 12, wherein, The printing device includes a first processing head assembly, a second processing head assembly, a third processing head assembly, and a fourth processing head assembly respectively provided with squeegees. The controlling the printing device to move from the first side of the stencil to the second side opposite to the first side to complete the first paste deposition and the second paste deposition includes: Lowering the squeegees of the first processing head assembly and the third processing head assembly to contact the surface of the stencil surface; The squeegees of the second processing head assembly and the fourth processing head assembly do not contact the surface of the stencil; Controlling the printing device to move from the first side of the stencil to the second side opposite to the first side, and completing the first paste deposition by using the squeegee of the third processing head assembly, and completing the second paste deposition by using the squeegee of the first processing head assembly.

14. The method according to claim 13, wherein, The first processing head assembly, the second processing head assembly, the third processing head assembly, and the fourth processing head assembly are sequentially arranged along the moving direction of the printing device.

15. The method according to claim 13, wherein, The amount of paste deposited on the substrate to be printed by the squeegee of the third processing head assembly during the first paste deposition is less than the amount of paste deposited on the substrate to be printed by the squeegee of the first processing head assembly.

16. The method according to claim 13, wherein, The force exerted on the stencil by the squeegee of the third processing head assembly during the first paste deposition is less than the force exerted on the stencil by the squeegee of the first processing head assembly during the second paste deposition.

17. The method according to claim 13, further comprising: After printing is completed, replacing another substrate to be printed; Controlling the printing device to move from the second side of the stencil to the first side to complete the first paste deposition and the second paste deposition on another substrate to be printed.

18. The method according to claim 17, wherein The controlling the printing device to move from the second side of the stencil to the first side to complete the first paste deposition and the second paste deposition on another substrate to be printed includes: Lifting the squeegees of the first processing head assembly and the third processing head assembly to not contact the surface of the stencil; lowering the squeegees of the second processing head assembly and the fourth processing head assembly to contact the surface of the stencil; Controlling the printing device to move from the second side of the stencil to the first side, and completing the first paste deposition by using the squeegee of the second processing head assembly, and completing the second paste deposition by using the squeegee of the fourth processing head assembly. The amount of paste deposited on the substrate to be printed by the squeegee of the second processing head assembly is less than the amount of paste deposited on the substrate to be printed by the squeegee of the fourth processing head assembly.

19. The method according to claim 18, wherein ​ 20. The method according to claim 13, wherein The doctor blades of the first processing head assembly and the fourth processing head assembly are made of a first material, and the doctor blades of the second processing head assembly and the third processing head assembly are made of a second material.

21. The method according to claim 20, wherein, The hardness of the second material is greater than that of the first material.

22. The method according to claim 21, wherein The doctor blades of the first processing head assembly and the fourth processing head assembly are both rubber strip doctor blades; the doctor blades of the second processing head assembly and the third processing head assembly are both steel doctor blades.

23. The method according to claim 18, wherein The force exerted by the doctor blade of the second processing head assembly on the stencil during the first slurry deposition is less than the force exerted by the doctor blade of the fourth processing head assembly on the stencil during the second slurry deposition.

24. The method according to claim 18, wherein During the first slurry deposition, the angle between the doctor blade of the third processing head assembly and the stencil is 30 to 90 degrees; the angle between the doctor blade of the second processing head assembly and the stencil is 30 to 90 degrees; During the second slurry deposition, the angle between the doctor blade of the first processing head assembly and the stencil is 30 to 90 degrees; the angle between the doctor blade of the fourth processing head assembly and the stencil is 30 to 90 degrees.

25. The method according to claim 12, wherein, The printing device includes a first processing head assembly and a second processing head assembly each with a doctor blade; Controlling the printing device to move from the first side of the stencil to the second side opposite the first side to complete the first slurry deposition and the second slurry deposition includes: Lowering the doctor blades of the first processing head assembly and the second processing head assembly to contact the surface of the stencil; The slurry is located on the stencil, and the slurry is respectively arranged corresponding to the doctor blades of the first processing head assembly and the second processing head assembly, and the slurry is respectively in front of the moving directions of the doctor blades of the first processing head assembly and the second processing head assembly; Controlling the printing device to move from the first side of the stencil to the second side opposite the first side, and using the doctor blade of the second processing head assembly to complete the first slurry deposition and using the doctor blade of the first processing head assembly to complete the second slurry deposition.

26. The method according to claim 25, further comprising: After printing is completed, replacing another substrate to be printed; The stencil is located above another substrate to be printed; Adjusting the printing device so that the slurry is respectively in front of the moving directions of the doctor blades of the first processing head assembly and the second processing head assembly to be; Controlling the printing device to move from the second side of the stencil to the first side to complete the first slurry deposition and the second slurry deposition on the said another substrate to be printed.

27. The method according to claim 2, wherein The controlling the printing device to move on the stencil includes: Controlling the printing device to move from the first side of the stencil to the second side opposite the first side to achieve the first slurry deposition and the first overcoating slurry; Controlling the printing device to move from the second side of the stencil to the first side to achieve the second slurry deposition and the second overcoating slurry; during the second slurry deposition, a second deposited slurry is formed on the upper surface of the substrate to be printed, and at least part of the second deposited slurry is stacked on the first deposited slurry.

28. The method according to claim 27, wherein, The printing device includes a first processing head assembly with an ink doctor blade, a second processing head assembly with a doctor blade, a third processing head assembly with a doctor blade, and a fourth processing head assembly with an ink doctor blade; The achieving the first slurry deposition and the first overcoating slurry includes: Lower the squeegee of the first processing head assembly and the doctor blade of the third processing head assembly so that the doctor blade of the third processing head assembly contacts the surface of the stencil; The squeegee of the second processing head assembly and the ink knife of the fourth processing head assembly do not contact the surface of the stencil; Control the printing device to move from the first side to the second side of the stencil; Use the doctor blade of the third processing head assembly to achieve paste deposition and form a first deposited paste on the upper surface of the substrate to be printed; Use the ink knife of the first processing head assembly to achieve the first paste coating on the stencil.

29. The method according to claim 28, wherein The implementation of the second paste deposition and the second paste coating includes: Lower the squeegee of the second processing head assembly and the ink knife of the fourth processing head assembly so that the squeegee of the second processing head assembly contacts the surface of the stencil; Raise the ink knife of the first processing head assembly and the doctor blade of the third processing head assembly, and neither of them contacts the surface of the stencil; Control the printing device from the Second side to the first side direction of the stencil, use the squeegee of the second processing head assembly to achieve paste deposition, and form a second deposited paste on the upper surface of the substrate to be printed, and at least part of the second deposited paste is stacked on the first deposited paste; Use the ink knife of the fourth processing head assembly to achieve the second paste coating on the stencil.

30. The method according to claim 12, wherein, The printing device includes a first processing head assembly with a squeegee, a second processing head assembly with an ink knife, a third processing head assembly with a squeegee, and a fourth processing head assembly with an ink knife.

31. The method according to claim 30, wherein, The first processing head assembly, the second processing head assembly, the third processing head assembly, and the fourth processing head assembly are arranged in sequence along the moving direction of the printing device.

32. The method according to claim 31, wherein, The control of the printing device to move from the first side to the second side of the stencil to complete the first paste deposition and the second paste deposition on the substrate to be printed includes: Lower the squeegee of the first processing head assembly and the squeegee of the third processing head assembly to contact the surface of the stencil; Control the printing device to move from the first side to the second side of the stencil, use the squeegee of the third processing head assembly to complete the first paste deposition, use the squeegee of the first processing head assembly to complete the second paste deposition, and at least part of the second deposited paste is stacked on the first deposited paste.

33. The method according to claim 32, wherein After completing the first paste deposition and the second paste deposition, it further includes: Raise the squeegee of the first processing head assembly and the squeegee of the third processing head assembly so that they do not contact the surface of the stencil, and lower the ink knife of the second processing head assembly and the ink knife of the fourth processing head assembly; Control the printing device to move from the second side to the first side of the stencil, and use the ink knife of the second processing head assembly and the ink knife of the fourth processing head assembly to complete the paste coating.

34. The method according to claim 2, wherein, There is no heat treatment process between the two paste deposition processes.

35. A printing device, the printing device adopts the method of screen printing on a substrate as described in claims 1-34.

36. A solar cell, the solar cell is prepared and formed by adopting the method of screen printing on a substrate as described in claims 1-34.

37. A solar cell module, the solar cell module is prepared by adopting a plurality of solar cells as described in claim 36.

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