Method for screen printing on a substrate, printing apparatus and solar cell

Abstract

The application discloses a method for screen printing on a substrate, a printing device and a solar cell, and aims to improve printing efficiency and obtain good printing effect. The method comprises the following steps: transmitting a substrate to be printed to a printing station; moving a screen plate to a predetermined printing position, the screen plate being located above the substrate to be printed, and paste being located on the screen plate; and controlling a printing device to move on the screen plate, so as to deposit the paste on the same surface of the substrate to be printed at least twice, and complete printing.

Description

Technical Field

[0001] This invention relates to printing technology for batteries, and more specifically, to a method, printing equipment, and solar cell for printing on a substrate screen. Background Technology

[0002] Currently, silicon-based heterojunction solar cells are a common high-efficiency solar cell technology. The transparent conductive film (TCO), as a lateral carrier transport layer, is an essential component of silicon-based heterojunction solar cells. Silver grid electrodes are formed on the TCO using screen printing. Overprinting is typically used to fabricate the silver grid electrodes. To obtain grid lines with a high aspect ratio, existing technologies employ two printing stations. After the first screen printing on the TCO, the grid moves to the second printing station. In the second station, a second screen printing is performed on the TCO, forming a secondary deposition paste. After these two printing processes, the grid lines achieve a high aspect ratio. Aspect ratio refers to the ratio of the grid line's height to its width. Existing screen printing technologies typically produce grid lines with an aspect ratio below 24%. Furthermore, existing screen printing techniques are characterized by long processing times and low efficiency. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method, printing equipment and solar cell for printing on a substrate screen, thereby improving printing efficiency and obtaining good printing results.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] Firstly, this solution provides a method for printing on a substrate using a screen printing plate, including:

[0006] The substrate to be printed is transferred to the printing station;

[0007] Move the screen to the predetermined printing position, with the screen above the substrate to be printed and the paste on the screen.

[0008] The printing device is controlled to move on the screen, and the paste is deposited on the same substrate at least twice to complete the printing.

[0009] As a preferred example, printing is completed by depositing paste twice on the same substrate surface.

[0010] As a preferred example, the control of the printing device moving 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 the first slurry deposition and form 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 to complete the second slurry deposition and form a second deposited slurry on the upper surface of the substrate to be printed, wherein the second deposited slurry is at least partially stacked on the first deposited slurry.

[0011] As a preferred embodiment, the printing apparatus includes a first processing head assembly equipped with a squeegee and a second processing head assembly equipped with a squeegee; in the first slurry deposition, the squeegee of the first processing head assembly descends and contacts the screen surface, while the squeegee of the second processing head assembly does not contact the screen surface, and the first slurry deposition is completed using the squeegee of the first processing head assembly; in the second slurry deposition, the squeegee of the second processing head assembly descends and contacts the screen surface; the squeegee of the first processing head assembly rises and does not contact the screen surface; the second slurry deposition is completed using the squeegee of the second processing head assembly.

[0012] As a preferred example, 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.

[0013] 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.

[0014] 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.

[0015] As a preferred example, the force exerted by the scraper of the first processing head assembly on the screen plate during the first slurry deposition is less than the force exerted by the scraper of the second processing head assembly on the screen plate during the second slurry deposition.

[0016] 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.

[0017] As a preferred example, the control of the printing device moving 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, 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 to apply a coating slurry on the screen; and controlling the printing device to move from the first side of the screen to the second side to complete a second slurry deposition, forming a second deposited slurry on the upper surface of the substrate to be printed, wherein the second deposited slurry is at least partially stacked on the first deposited slurry.

[0018] As a preferred embodiment, the printing apparatus includes a first processing head assembly equipped with an ink blade and a second processing head assembly equipped with a doctor blade; in the first coating of the slurry, the ink blade of the first processing head assembly is lowered, while the doctor blade of the second processing head assembly does not contact the screen surface, and the coating of the slurry is completed using the ink blade of the first processing head assembly; in the first slurry deposition and the second slurry deposition, the doctor blade of the second processing head assembly is lowered and contacts the screen surface; the ink blade of the first processing head assembly is raised and does not contact the screen surface; the slurry deposition is completed using the doctor blade of the second processing head assembly.

[0019] As a preferred example, the control of the printing device moving 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.

[0020] As a preferred embodiment, the printing apparatus includes a first processing head assembly, a second processing head assembly, a third processing head assembly, and a fourth processing head assembly, each equipped with a squeegee. Controlling the printing apparatus to move from a first side of the screen to a second side opposite to the first side to complete the first and second slurry depositions includes: lowering the squeegees of the first and third processing head assemblies to contact the screen surface; the squeegees of the second and fourth processing head assemblies not contacting the screen surface; controlling the printing apparatus to move from the first side of the screen to the second side opposite to the first side, using the squeegee of the third processing head assembly to complete the first slurry deposition, and using the squeegee of the first processing head assembly to complete the second slurry deposition.

[0021] As a preferred embodiment, the first processing head assembly, the second processing head assembly, the third processing head assembly, and the fourth processing head assembly are arranged sequentially along the moving direction of the printing device.

[0022] As a preferred example, the amount of paste deposited onto the substrate by the doctor blade movement of the third processing head assembly is less than the amount of paste deposited onto the substrate by the doctor blade movement of the first processing head assembly.

[0023] As a preferred example, the force exerted by the scraper of the third processing head assembly on the screen plate during the first slurry deposition is less than the force exerted by the scraper of the first processing head assembly on the screen plate during the second slurry deposition.

[0024] 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 of the screen to the first side to complete the first and second slurry deposition on the other substrate to be printed.

[0025] As a preferred example, the controlled printing device moves from the second side of the screen to the first side to complete the first and second slurry depositions on another substrate to be printed, including: raising the squeegee of the first processing head assembly and the squeegee of the third processing head assembly so that they do not contact the screen surface; lowering the squeegee of the second processing head assembly and the squeegee of the fourth processing head assembly so that they contact the screen surface; controlling the printing device to move from the second side of the screen to the first side, using the squeegee of the second processing head assembly to complete the first slurry deposition, and using the squeegee of the fourth processing head assembly to complete the second slurry deposition.

[0026] As a preferred example, the amount of paste deposited onto the substrate by the doctor blade movement of the second processing head assembly is less than the amount of paste deposited onto the substrate by the doctor blade movement of the fourth processing head assembly.

[0027] As a preferred example, the scrapers of the first processing head assembly and the fourth processing head assembly are made of a first material, while the scrapers of the second processing head assembly and the third processing head assembly are made of a second material.

[0028] As a preferred example, the hardness of the second material is greater than that of the first material.

[0029] As a preferred embodiment, the scrapers of the first processing head assembly and the fourth processing head assembly are both rubber strip scrapers; the scrapers of the second processing head assembly and the third processing head assembly are both steel scrapers.

[0030] As a preferred example, the force exerted by the scraper of the second processing head assembly on the screen plate during the first slurry deposition is less than the force exerted by the scraper of the fourth processing head assembly on the screen plate during the second slurry deposition.

[0031] As a preferred example, in the first slurry deposition, the angle between the scraper and the screen of the third processing head assembly is 30 to 90 degrees; the angle between the scraper and the screen of the second processing head assembly is 30 to 90 degrees; in the second slurry deposition, the angle between the scraper and the screen of the first processing head assembly is 30 to 90 degrees; and the angle between the scraper and the screen of the fourth processing head assembly is 30 to 90 degrees.

[0032] As a preferred embodiment, the printing apparatus includes a first processing head assembly and a second processing head assembly, each equipped with a squeegee; controlling the printing apparatus to move from a first side of the screen to a second side opposite to the first side to complete the first and second slurry depositions includes: lowering the squeegees of the first and second processing head assemblies to contact the screen surface; the slurry is located on the screen, with the slurry corresponding to the squeegees of the first and second processing head assemblies respectively, and the slurry is located in front of the squeegees of the first and second processing head assemblies in their respective moving directions; controlling the printing apparatus to move from the first side of the screen to the second side opposite to the first side, using the squeegee of the second processing head assembly to complete the first slurry deposition, and using the squeegee of the first processing head assembly to complete the second slurry deposition.

[0033] As a preferred example, the method further includes: after printing is completed, replacing another substrate to be printed; the screen is positioned above the other substrate to be printed; adjusting the printing device so that the paste is positioned in front of the squeegee of the first processing head assembly and the squeegee of the second processing head assembly in the direction to be moved; controlling the printing device to move from the second side of the screen to the first side to complete the first paste deposition and the second paste deposition on the other substrate to be printed.

[0034] As a preferred example, the control of the printing device moving 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 coating slurry; 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 coating slurry; 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.

[0035] As a preferred embodiment, the printing apparatus includes a first processing head assembly with an ink 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 blade; the process of achieving the first paste deposition and the first coating paste includes: lowering the ink blade 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 screen surface; neither the doctor blade of the second processing head assembly nor the ink blade of the fourth processing head assembly contacts the screen surface; controlling the printing apparatus to move from the first side of the screen to the second side; using the doctor blade of the third processing head assembly to achieve paste deposition, forming the first deposited paste on the surface of the substrate to be printed; and using the ink blade of the first processing head assembly to achieve the first coating paste on the screen.

[0036] As a preferred example, the second slurry deposition and second coating slurry are achieved by: lowering the squeegee of the second processing head assembly and the ink blade of the fourth processing head assembly so that the squeegee of the second processing head assembly contacts the screen surface; raising the ink blade of the first processing head assembly and the squeegee of the third processing head assembly so that neither contacts the screen surface; controlling the printing device to move from the second side to the first side of the screen, using the squeegee of the second processing head assembly to achieve slurry deposition, forming a second deposited slurry on the surface of the substrate to be printed, and the second deposited slurry at least partially stacked on the first deposited slurry; and using the ink blade of the fourth processing head assembly to achieve a second coating slurry on the screen.

[0037] As a preferred example, the printing apparatus includes a first processing head assembly with a doctor blade, a second processing head assembly with an ink blade, a third processing head assembly with a doctor blade, and a fourth processing head assembly with an ink blade.

[0038] As a preferred embodiment, the first processing head assembly, the second processing head assembly, the third processing head assembly, and the fourth processing head assembly are arranged sequentially along the moving direction of the printing device.

[0039] As a preferred example, the controlled printing device moves from the first side to the second side of the screen to complete the first and second slurry deposition on the substrate to be printed, including: lowering the squeegee of the first processing head assembly and the squeegee of the third processing head assembly to contact the screen surface; controlling the printing device to move from the first side to the second side of the screen, using the squeegee of the third processing head assembly to complete the first slurry deposition, and using the squeegee of the first processing head assembly to complete the second slurry deposition, wherein the second deposited slurry is at least partially stacked on the first deposited slurry.

[0040] As a preferred example, after completing the first and second slurry depositions, the method further includes: raising the squeegee of the first processing head assembly and the squeegee of the third processing head assembly so as not to contact the screen surface; lowering the ink blade of the second processing head assembly and the ink blade of the fourth processing head assembly; controlling the printing device to move from the second side to the first side of the screen; and using the ink blades of the second and fourth processing head assemblies to complete the slurry coating.

[0041] As a preferred example, there is no heat treatment process between the two slurry deposition processes.

[0042] Secondly, this solution provides a printing device that employs the aforementioned method of printing on a substrate using a screen printing plate.

[0043] Thirdly, this solution provides a solar cell, which is prepared by the aforementioned method of printing on a substrate using a screen printing plate.

[0044] Fourthly, this solution provides a solar cell module, which is formed by fabricating multiple of the aforementioned solar cells.

[0045] Compared with existing technologies, the method of this invention can improve work efficiency and achieve good printing results. The method of this embodiment includes: transferring the substrate to be printed to the printing station; moving the screen to a predetermined printing position, with the screen above the substrate and the ink on the screen; controlling the printing device to move on the screen, depositing ink at least twice on the same substrate surface to complete the printing. By achieving at least two ink deposits at the same station, work efficiency is improved, and the resulting grid line aspect ratio is high, reaching 0.5 or higher. Attached Figure Description

[0046] Figure 1 This is a schematic first process diagram of the first preferred embodiment of the present invention;

[0047] Figure 2 This is a schematic second process diagram of the first preferred embodiment of the present invention;

[0048] Figure 3 This is a schematic first process diagram of the second preferred embodiment of the present invention;

[0049] Figure 4 This is a schematic second process diagram of the second preferred embodiment of the present invention;

[0050] Figure 5 This is an illustrative third process diagram of the second preferred embodiment of the present invention;

[0051] Figure 6 This is a schematic first process diagram of the third preferred embodiment of the present invention;

[0052] Figure 7 This is a schematic second process diagram of the third preferred embodiment of the present invention;

[0053] Figure 8 This is a schematic first process diagram of the fourth preferred embodiment of the present invention;

[0054] Figure 9 This is a schematic second process diagram of the fourth preferred embodiment of the present invention;

[0055] Figure 10 This is a schematic first process diagram of the fifth preferred embodiment of the present invention;

[0056] Figure 11 This is a schematic second process diagram of the fifth preferred embodiment of the present invention;

[0057] Figure 12This is a schematic first process diagram of the sixth preferred embodiment of the present invention;

[0058] Figure 13 This is a schematic second process diagram of the sixth preferred embodiment of the present invention;

[0059] Figure 14 This is a schematic diagram of the printing section in this invention;

[0060] Figure 15 This is a schematic diagram of the printing apparatus in this invention. Detailed Implementation

[0061] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0062] This application has a wide range of applications; as one example, the substrate is a silicon-based solar cell with a transparent conductive layer formed thereon. Printing on the substrate involves printing grid electrodes onto the transparent conductive layer.

[0063] This invention provides a method for printing on a substrate using a screen printing plate, comprising:

[0064] Step 10: Transfer the substrate to be printed to the printing station. For example, the substrate can be transferred to the printing station via a conveyor belt, rotary table, or other conveying method. Printing is then performed on the substrate at the printing station.

[0065] Step 20: Move the screen to the predetermined printing position, with the screen above the substrate to be printed and the ink on the screen. After the substrate to be printed is transferred to the printing station, move the screen to the predetermined printing position so that the screen is above the substrate.

[0066] Step 30: Control the printing device to move on the screen, depositing paste at least twice on the same substrate to complete the printing process. During printing, the paste is pushed and displaced by the printing device, allowing it to be deposited onto the substrate through the screen.

[0067] Compared to existing technologies that complete printing with a single paste deposition on the substrate, this embodiment involves at least two paste depositions on the same substrate surface to complete the printing process. Figure 14 As shown, the printing section formed on the upper surface of the same substrate includes a first deposition paste 20 located below and a second deposition paste 19 located above. By increasing the number of paste depositions at the same station, the aspect ratio of the printed grid lines can reach over 25%. Furthermore, compared to existing multi-station printing, the method of this embodiment completes multiple paste depositions at the same station, significantly improving work efficiency.

[0068] In existing technologies, after the first printing on a transparent conductive film layer using a screen, the first deposited paste needs to be heat-treated, such as baked, before proceeding to the second printing station. At the second printing station, a second printing is performed on the transparent conductive film layer using a screen, forming a second deposited paste. In the above embodiment, there is no heat treatment process between the two paste deposition processes. This method eliminates the existing paste drying and heat treatment process, simplifying the process and improving efficiency.

[0069] As a preferred example, printing is completed by depositing paste twice on the upper surface of the same substrate. Two paste deposits allow for a higher aspect ratio in the grid lines. Reducing the number of paste deposits while maintaining printing quality improves work efficiency, simplifies the structure of the printing equipment, and lowers manufacturing costs.

[0070] The printing apparatus described in this embodiment, such as Figure 15 As shown, the device includes a processing head assembly, a lifting device 23, a base 21, and a horizontal moving device 22. The processing head assembly and the lifting device 23 are connected, the lifting device 23 is connected to the base 21, and the base 21 is connected to the horizontal moving device 22. The processing head assemblies have the same main structure; for example, the first, second, third, and fourth processing head assemblies described herein have the same main structure. The processing head assembly includes a support and a cutting tool connected to the bottom of the support. The lifting device moves the processing head assembly up and down, and the horizontal moving device 22 moves the processing head assembly in a horizontal plane, for example, left and right. Preferably, the horizontal moving device 22 moves all processing head assemblies synchronously in a horizontal plane. The cutting tool can be a doctor blade or an ink blade. Multiple processing head assemblies can be provided in the same printing device. Figure 15 As shown, the printing unit has two processing head assemblies. A doctor blade or an ink blade is selected depending on the actual situation. The same printing unit can move all the blades horizontally synchronously, and the lifting and lowering of each individual processing head assembly can also be adjusted separately.

[0071] The first preferred example is, for example: Figure 1 As shown, the printing apparatus includes a first processing head assembly equipped with a doctor blade 5 and a second processing head assembly equipped with a doctor blade 6. The first processing head assembly and the second processing head assembly are arranged along the moving direction of the printing apparatus.

[0072] In step 30, controlling the printing device to move on the screen includes:

[0073] Step 3011 controls the printing device to move from the first side of the screen 2 to the second side opposite to the first side, completing the first slurry deposition and forming the first deposited slurry on the surface of the substrate to be printed.

[0074] The first and second sides are two opposite sides of the mesh panel. For example... Figure 1 As shown by the arrow, it moves from the first side of the mesh to the second side. Figure 2 As indicated by the arrows, the stencil moves from the second side to the first side. During the first slurry deposition, the scraper of the first processing head assembly descends and contacts the stencil surface, while the scraper of the second processing head assembly does not contact the stencil surface. The first slurry deposition is completed using the scraper of the first processing head assembly. Figure 1 As shown, in the first paste deposition, only the squeegee 5 of the first processing head assembly contacts the stencil 2. The paste 4 moves on the surface of the stencil 2 as the squeegee 5 of the first processing head assembly moves. During the movement of the paste 4, some paste is deposited onto the upper surface of the substrate 1 to be printed, forming the first deposited paste. In the first paste deposition, the squeegee 6 of the second processing head assembly does not contact the surface of the stencil 2, nor does it apply force to the paste.

[0075] Step 3012 controls the printing apparatus to move from the second side of the screen to the first side to complete the second paste deposition, forming a second deposited paste on the upper surface of the substrate to be printed, and the second deposited paste is at least partially stacked on the first deposited paste.

[0076] In the second slurry deposition, such as Figure 2 As shown, the squeegee 6 of the lowered second processing head assembly contacts the surface of the stencil 2; the squeegee 5 of the uppered first processing head assembly does not contact the surface of the stencil 2; the second paste deposition is completed using the squeegee 6 of the second processing head assembly. During the second paste deposition, the squeegee 6 of the second processing head assembly contacts the surface of the stencil 2. The squeegee 6 of the second processing head assembly moves the paste 4 across the surface of the stencil 2. During this movement, a portion of the paste is deposited onto the substrate 1 to be printed, forming the second deposited paste. The second deposited paste at least partially overlaps the first deposited paste.

[0077] In this embodiment, the first deposited paste acts as a substrate. The second deposited paste and the first deposited paste together form the printing section. In this embodiment, the printing apparatus moves back and forth once between the first and second sides of the screen, for a total of two moves, thereby achieving two paste deposits on the same substrate to be printed.

[0078] In this embodiment, the amount of paste deposited on the substrate in the first paste deposition is greater than or equal to the amount deposited on the substrate in the second paste deposition. However, preferably, the amount of paste deposited on the substrate in the first paste deposition is less than the amount deposited on the substrate in the second paste deposition. The smaller amount of paste in the first paste deposition serves as a substrate. The larger amount of paste in the second paste deposition fills the mesh openings of the stencil, achieving a higher aspect ratio for the printed grid lines. Simultaneously, the printed grid lines have a more stable structure and are less prone to breakage.

[0079] 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. This results in a smaller contact area between the scraper of the first processing head assembly and the stencil than the contact area between the scraper of the second processing head assembly and the stencil, allowing the scraper of the second processing head assembly to scrape off 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 merely preferred options; those skilled in the art can also use scrapers made of other materials.

[0080] In this embodiment, the force exerted by the squeegee of the first processing head assembly on the stencil during the first slurry deposition is equal to or greater than the force exerted by the squeegee of the second processing head assembly on the stencil during the second slurry deposition. However, preferably, the force exerted by the squeegee of the first processing head assembly on the stencil during the first slurry deposition is less than the force exerted by the squeegee of the second processing head assembly on the stencil during the second slurry deposition. This results in a smaller amount of slurry in the first deposition and a larger amount of slurry in the second deposition. The printed grid lines have a more stable structure and are less prone to breakage.

[0081] In this embodiment, preferably, during the first slurry deposition, the angle between the scraper of the first processing head assembly and the screen is 30 to 90 degrees; during the second slurry deposition, the angle between the scraper of the second processing head assembly and the screen is 30 to 90 degrees.

[0082] In a second preferred embodiment, the printing apparatus includes a first processing head assembly equipped with an ink knife and a second processing head assembly equipped with a doctor blade. The first and second processing head assemblies are arranged along the moving direction of the printing apparatus.

[0083] In step 30, controlling the printing device to move on the screen specifically includes:

[0084] Step 3021 controls the printing apparatus to move from the first side of the screen to the second side opposite to the first side, completing the first paste deposition and forming the first deposited paste on the surface of the substrate to be printed. Figure 3 As shown, the printing apparatus moves from the left side to the right side of the screen. The squeegee 8 of the second processing head assembly descends and contacts the surface of the screen 2; the ink blade 7 of the first processing head assembly rises and does not contact the surface of the screen 2. The squeegee 8 of the second processing head assembly acts on the paste already coated on the screen, causing some of the paste to detach from the screen and fall onto the substrate to be printed below the screen, forming the first deposition of paste.

[0085] Step 3022 controls the printing device to move from the second side of the screen to the first side, coating the screen with paste. For example... Figure 4As shown, the printing apparatus moves from the right side to the left side of the screen 2. The inking blade 7 of the first processing head assembly descends, no longer contacting the surface of the screen 2; the squeegee 8 of the second processing head assembly rises, also no longer contacting the surface of the screen 2. The inking blade 7 moves the ink 4 in front of it across the surface of the screen 2. The ink 4 is then recoated onto the surface of the screen 2 using the inking blade 7 of the first processing head assembly, completing the ink coating process.

[0086] Step 3023 controls the printing apparatus to move from the first side of the screen to the second side, completing the second paste deposition, forming a second deposited paste on the surface of the substrate to be printed, and the second deposited paste at least partially stacks on the first deposited paste. Figure 5 As shown, the printing apparatus moves from left to right of the screen. The squeegee 8 of the second processing head assembly descends and contacts the surface of the screen 2; the ink blade 7 of the first processing head assembly rises and does not contact the surface of the screen 2. The squeegee 8 of the second processing head assembly acts on the paste already coated on the screen, causing some of the paste to detach from the screen and fall onto the substrate to be printed below the screen, forming a second deposited paste. The second deposited paste at least partially overlaps the first deposited paste.

[0087] Prior to step 3021, the method may further include: controlling the printing device to move from the second side of the screen to the first side, and applying a coating paste to the screen.

[0088] In the second preferred embodiment, the ink scalpel and the squeegee are used together. Before the squeegee operates, the ink scalpel coats the screen with paste. This ensures that there is sufficient paste on the screen when the squeegee operates. In this second preferred embodiment, the printing apparatus needs to move back and forth on each side a total of four times to form the first and second paste deposits on the substrate to be printed, thus completing the printing process.

[0089] It should be noted that in this scheme, three or more slurry depositions can also be performed, but this will not be discussed further here.

[0090] In a third preferred embodiment, the printing apparatus includes a first processing head assembly with a 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 a doctor blade. The first, second, third, and fourth processing head assemblies are arranged sequentially along the direction of movement of the printing apparatus.

[0091] In step 30, controlling the printing device to move on the screen specifically includes:

[0092] Step 3031 controls the printing apparatus to move from the first side of the screen to the second side opposite to the first side, completing 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 the second deposited paste is at least partially stacked on the first deposited paste. The completion of the first paste deposition and the second paste deposition includes:

[0093] Step 30311 as follows Figure 6 As shown, the scraper 9 of the first processing head assembly and the scraper 11 of the third processing head assembly descend and contact the surface of the screen plate 2; the scraper 10 of the second processing head assembly and the scraper 12 of the fourth processing head assembly do not contact the surface of the screen plate 2. In the direction of movement, slurry 4 is respectively provided in front of the scraper 9 of the first processing head assembly and in front of the scraper 11 of the third processing head assembly.

[0094] Step 30312 as follows Figure 6 As shown, the printing apparatus moves from the first side of the screen to the second side opposite to the first side, that is, from the left to the right as shown in the figure. The printing apparatus is sequentially equipped with a first processing head assembly with a squeegee 9, a second processing head assembly with a squeegee 10, a third processing head assembly with a squeegee 11, and a fourth processing head assembly with a squeegee 12 along the direction of movement. The first paste deposition is completed using the squeegee 11 of the third processing head assembly, and the second paste deposition is completed using the squeegee 9 of the first processing head assembly. The squeegee 11 of the third processing head assembly operates before the squeegee 9 of the first processing head assembly. The squeegee 11 of the third processing head assembly moves the paste 4 on the surface of the screen 2. During the movement, part of the paste 4 is deposited onto the substrate 1 to be printed, forming the first deposited paste. The squeegee 9 of the first processing head assembly moves the paste 4 on the surface of the screen 2. During the movement, part of the paste is deposited onto the substrate 1 to be printed, forming the second deposited paste. The second deposited paste is at least partially stacked on top of the first deposited paste.

[0095] In the above method, the printing device moves from the first side of the screen to the second side opposite to the first side, completing the first and second paste depositions. During this process, the printing device moves from one side of the screen to the other, completing two paste depositions. Similarly, in the third preferred embodiment, the travel path of the printing device is half that of the first preferred embodiment and one-quarter that of the second preferred embodiment. In this preferred embodiment, the travel path of the printing device is shorter, greatly improving work efficiency.

[0096] In step 30312, the amount of paste deposited onto the substrate by the squeegee movement of the third processing head assembly is greater than or equal to the amount of paste deposited onto the substrate by the squeegee movement of the first processing head assembly. Preferably, the amount of paste deposited onto the substrate by the squeegee movement of the third processing head assembly is less than the amount of paste deposited onto the substrate by the squeegee movement of the first processing head assembly. The first paste deposition involves a smaller amount of paste, serving as a substrate. The second paste deposition involves a larger amount of paste, which can fill the mesh openings of the stencil, achieving a higher aspect ratio for the printed grid lines.

[0097] In this embodiment, the force exerted by the squeegee of the third processing head assembly on the stencil during the first slurry deposition is greater than or equal to the force exerted by the squeegee of the first processing head assembly on the stencil during the second slurry deposition. However, preferably, the force exerted by the squeegee of the third processing head assembly on the stencil during the first slurry deposition is less than the force exerted by the squeegee of the first processing head assembly on the stencil during the second slurry deposition. This results in a smaller amount of slurry in the first deposition and a larger amount of slurry in the second deposition. The printed grid lines have a more stable structure and are less prone to breakage.

[0098] In the third preferred embodiment, step 3032 is performed after step 3031. Step 3032 includes:

[0099] After printing is completed in step 30321, replace the substrate with another substrate to be printed.

[0100] Step 30322 as follows Figure 7 As shown, the printing device is controlled to move from the second side of the screen to the first side to complete the first and second slurry depositions on another substrate to be printed.

[0101] In step 3031, the printing apparatus moves from the first side to the second side of the screen to complete the printing on the substrate to be printed. Then, in step 3032, the printing apparatus moves from its resting position, i.e., the second side of the screen, to the first side of the screen, and completes the printing on another substrate to be printed. Step 3032 continues the movement of the printing apparatus in step 3031, and during the movement of the printing apparatus, two paste depositions are achieved on the other substrate to be printed. This greatly improves the working efficiency of the printing apparatus.

[0102] In the first preferred embodiment, the printing device reciprocates once to complete the printing of one substrate. In the second preferred embodiment, the printing device reciprocates twice to complete the printing of one substrate. In the third preferred embodiment, the printing device reciprocates once to complete the printing of two substrates.

[0103] Furthermore, the printing apparatus is sequentially provided along the moving direction with a first processing head assembly with a doctor blade 9, a second processing head assembly with a doctor blade 10, a third processing head assembly with a doctor blade 11, and a fourth processing head assembly with a doctor blade 12. After the first and second slurry depositions on the substrate to be printed are completed, the slurry is located on the side of the doctor blade 9 of the first processing head assembly and the doctor blade 11 of the third processing head assembly near the second side of the screen, respectively. Therefore, before performing the printing process on another substrate to be printed, the doctor blades 9 and 11 of the first and third processing head assemblies can be raised, and the doctor blades 10 and 12 of the second and fourth processing head assemblies can be lowered. At this time, the slurry is located on the side of the doctor blades 10 and 12 of the second and fourth processing head assemblies in the direction to be moved, respectively. Figure 7 As shown, this setup simplifies the process and improves printing efficiency.

[0104] Specifically, in step 30322, the printing apparatus is controlled to move from the second side of the screen to the first side, completing the first and second paste depositions on another substrate to be printed, such as... Figure 7 As shown, it includes:

[0105] Step 303221: Raise the scraper 9 of the first processing head assembly and the scraper 11 of the third processing head assembly so that they do not contact the surface of the mesh plate 2; lower the scraper 10 of the second processing head assembly and the scraper 12 of the fourth processing head assembly so that they contact the surface of the mesh plate 2.

[0106] Step 303222: Control the printing device to move from the second side of the screen to the first side, complete the first slurry deposition using the doctor blade 10 of the second processing head assembly, and complete the second slurry deposition using the doctor blade 12 of the fourth processing head assembly.

[0107] The squeegee 10 of the second processing head assembly operates before the squeegee 12 of the fourth processing head assembly. The squeegee 10 of the second processing head assembly moves the ink paste across the screen surface. During this movement, a portion of the ink paste is deposited onto the substrate to be printed, forming the first deposited ink paste. The squeegee 12 of the fourth processing head assembly moves the ink paste across the screen surface 2. During this movement, a portion of the ink paste is deposited onto the substrate to be printed, forming the second deposited ink paste. The second deposited ink paste at least partially overlaps the first deposited ink paste.

[0108] In the above method, the printing apparatus moves from the second side of the screen to the first side to complete the first and second slurry deposition on another substrate to be printed.

[0109] In step 303222, the amount of paste deposited onto the substrate by the squeegee movement of the second processing head assembly is greater than or equal to the amount of paste deposited onto the substrate by the squeegee movement of the fourth processing head assembly. Preferably, the amount of paste deposited onto the substrate by the squeegee movement of the second processing head assembly is less than the amount of paste deposited onto the substrate by the squeegee movement of the fourth processing head assembly. The first paste deposition involves a smaller amount of paste, serving as a substrate. The second paste deposition involves a larger amount of paste, which can fill the mesh openings of the stencil, achieving a higher aspect ratio for the printed grid lines.

[0110] In a third preferred embodiment, the scrapers of the first and fourth processing head assemblies are made of a first material, while the scrapers of the second and third processing head assemblies are made of a second material. The first and second materials can be of the same material. However, preferably, the first and second materials are of different materials. Preferably, the hardness of the second material is greater than that of the first material. This results in a larger contact area between the scraper of the first processing head assembly and the stencil than the contact area between the scraper of the second processing head assembly and the stencil, allowing the scraper of the second processing head assembly to scrape off more slurry. For example, the scrapers of the first and fourth processing head assemblies are both rubber strip scrapers; the scrapers of the second and third processing head assemblies are both steel scrapers.

[0111] In step 303222, the force exerted by the squeegee of the second processing head assembly on the stencil during the first slurry deposition is greater than or equal to the force exerted by the squeegee of the fourth processing head assembly on the stencil during the second printing. However, preferably, the force exerted by the squeegee of the second processing head assembly on the stencil during the first printing is less than the force exerted by the squeegee of the fourth processing head assembly on the stencil during the second printing. The amount of slurry in the first slurry deposition is relatively small, serving as a substrate. The amount of slurry in the second slurry deposition is larger, which can fill the mesh openings of the stencil, achieving a higher aspect ratio for the printed grid lines. Simultaneously, the printed grid lines have a more stable structure and are less prone to breakage.

[0112] Preferably, in the first printing, the angle between the squeegee of the fifth processing head assembly and the screen is 30 to 90 degrees; the angle between the squeegee of the fourth processing head assembly and the screen is 30 to 90 degrees; in the second printing, the angle between the squeegee of the third processing head assembly and the screen is 30 to 90 degrees; and the angle between the squeegee of the sixth processing head assembly and the screen is 30 to 90 degrees.

[0113] In a fourth preferred embodiment, controlling the printing apparatus to move on a screen includes: controlling the printing apparatus to move from a first side of the screen to a second side opposite to the first side to complete a first paste deposition and a 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 the second deposited paste is at least partially stacked on the first deposited paste.

[0114] In a fourth preferred embodiment, the printing apparatus includes a first processing head assembly with a doctor blade 17 and a second processing head assembly with a doctor blade 18. The first and second processing head assemblies are arranged along the moving direction of the printing apparatus. The printing apparatus is controlled to move from a first side of the screen towards a second side opposite to the first side to complete the first and second slurry depositions, as shown below. Figure 8 As shown, it includes:

[0115] Step 3041: Lower the scraper 17 of the first processing head assembly and the scraper 18 of the second processing head assembly to contact the surface of the screen plate 2; the slurry 4 is located on the screen plate 2, and the slurry 4 is respectively positioned 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;

[0116] Step 3042 controls the printing device to move from the first side of the screen 2 to the second side opposite to the first side, and completes the first slurry deposition using the doctor blade 18 of the second processing head assembly, and completes the second slurry deposition using the doctor blade 17 of the first processing head assembly.

[0117] In the fourth preferred embodiment, the printing apparatus can complete two paste depositions on the same substrate by moving once.

[0118] After printing is complete, the method further includes:

[0119] After printing in step 3043 is completed, replace the substrate with another one to be printed.

[0120] Step 3044: The screen is positioned above another substrate to be printed; the printing apparatus is adjusted so that the paste 4 is positioned in front of the squeegee 17 of the first processing head assembly and the squeegee 18 of the second processing head assembly in the direction to be moved. Figure 9 As shown, the printing apparatus moves from the right side of the screen to the left side of the screen. At the starting position of the movement, i.e., on the right side of the screen, there is a paste 4 on the left side of the squeegee 17 of the first processing head assembly and the left side of the squeegee 18 of the second processing head assembly.

[0121] Step 3045 controls the printing device to move from the second side of the screen to the first side, completing the first and second slurry deposition on another substrate to be printed.

[0122] Similar to the third preferred embodiment, the printing apparatus in the fourth preferred embodiment also completes two ink depositions in a single stroke to finish the printing process. In the third preferred embodiment, when the printing apparatus changes direction, it is not necessary to adjust the horizontal position of the processing head assembly; simply raising or lowering the processing head assembly is sufficient. However, in the fourth preferred embodiment, when the printing apparatus changes direction, the horizontal position of the processing head assembly must first be adjusted so that the ink is positioned in front of the squeegee after the change in direction. This allows the squeegee to move the ink on the screen. After adjusting the horizontal position of the processing head assembly, it is then lowered to bring the squeegee into contact with the screen. Compared to the fourth preferred embodiment, the adjustment of the processing head assembly in the third preferred embodiment is simpler and more reliable.

[0123] The fifth preferred example, such as Figure 10 As shown, the printing apparatus includes a first processing head assembly with an ink blade 13, a second processing head assembly with a doctor blade 14, a third processing head assembly with a doctor blade 15, and a fourth processing head assembly with an ink blade 16. The first, second, third, and fourth processing head assemblies are arranged sequentially along the moving direction of the printing apparatus.

[0124] In step 30, controlling the printing device to move on the screen specifically includes:

[0125] Step 3051 controls the printing device to move from the first side of the screen to the second side opposite to the first side, thereby realizing the first slurry deposition and the first coating slurry.

[0126] Step 3052 controls the printing apparatus to move from the second side of the screen to the first side to achieve a second slurry deposition and a second coating slurry; 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.

[0127] In step 3051, the first slurry deposition and the first coating slurry are achieved, including: as follows Figure 10As shown, the ink blade 13 of the first processing head assembly and the doctor blade 15 of the third processing head assembly are lowered, so that the doctor blade 15 of the third processing head assembly contacts the surface of the screen 2, while the ink blade 13 of the first processing head assembly does not contact the surface of the screen 2; the doctor blades 14 of the second processing head assembly and the ink blade 16 of the fourth processing head assembly do not contact the surface of the screen 2; the printing device is controlled to move from the first side to the second side of the screen 2, with the ink blade 13 of the first processing head assembly located upstream of the doctor blade 15 of the third processing head assembly. The doctor blade 15 of the third processing head assembly is used to achieve paste deposition, forming the first deposited paste on the 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 screen 2 is less than the distance between the ink blade 16 of the fourth processing head assembly and the screen 2. The ink blade 13 of the first processing head assembly is used to achieve the first coating of paste on the screen 2.

[0128] In this embodiment, the squeegee 15 operates before the ink blade 13. The squeegee deposits the paste. After the squeegee forms the first deposited paste on the surface of the substrate 1 to be printed, the ink blade 13 coats the paste between the squeegee 15 and the ink blade 13 onto the screen, thus preparing for the next paste application.

[0129] Prior to step 3051, the method further includes: controlling the printing device to move on the screen and applying paste to the screen. At least one of the ink blades of the first processing head assembly and the fourth processing head assembly is lowered, without contacting the screen surface, and moves from one side of the screen to the other to achieve the application of paste to the screen.

[0130] In step 3052, the second slurry deposition and second coating slurry application include: as follows Figure 11 As shown, the squeegee 14 of the second processing head assembly and the ink blade 16 of the fourth processing head assembly are lowered, so that the squeegee 14 of the second processing head assembly contacts the surface of the screen 2, while the ink blade 16 of the fourth processing head assembly does not contact the surface of the screen 2. The ink blade 13 of the first processing head assembly and the squeegee 15 of the third processing head assembly are raised, neither of which contacts the surface of the screen 2. The printing device is controlled to move from the second side to the first side of the screen 2, with the ink blade 16 of the fourth processing head assembly positioned upstream of the squeegee 14 of the second processing head assembly. The slurry is deposited using the squeegee 14 of the second processing head assembly, forming a second deposited slurry on the surface of the substrate to be printed, and the second deposited slurry at least partially overlaps the first deposited slurry. During this process, the distance between the ink blade 16 of the fourth processing head assembly and the screen 2 is less than the distance between the ink blade 13 of the first processing head assembly and the screen 2, allowing the ink blade 16 of the fourth processing head assembly to achieve a second coating of slurry on the screen.

[0131] In the fifth preferred embodiment, step 3053 ends, meaning that two ink depositions are completed on the same substrate to be printed, thus completing the printing process. After step 3053, the process returns to step 3052 and repeats until printing is finished or the ink on the screen is used up, at which point ink is replenished.

[0132] In the fifth preferred embodiment, apart from the initial application of paste, the printing apparatus needs to move back and forth once each to complete the printing work on the substrate. In the second preferred embodiment, during one movement of the printing apparatus, for example, from the first side of the screen to the second side, only one of the squeegee and the ink knife is in operation. In the fifth preferred embodiment, during one movement of the printing apparatus, both the squeegee and the ink knife are in operation simultaneously.

[0133] The ink scalpel coats the slurry located between the doctor blade performing deposition and the ink scalpel onto the screen, thus preparing for the next slurry application. Compared to the second preferred embodiment, the fifth preferred embodiment improves work efficiency.

[0134] In the sixth preferred embodiment, the printing device can complete two paste depositions on the same substrate to be printed by moving once, and then the paste is coated by an ink knife;

[0135] In the sixth preferred example, such as Figure 12 As shown, the printing apparatus includes a first processing head assembly with a doctor blade 9, a second processing head assembly with an ink blade 24, a third processing head assembly with a doctor blade 11, and a fourth processing head assembly with an ink blade 25.

[0136] Preferably, the first processing head assembly, the second processing head assembly, the third processing head assembly, and the fourth processing head assembly are arranged sequentially along the moving direction of the printing device.

[0137] In the sixth preferred example, such as Figure 12 As shown, the controlled printing device moves from the first side to the second side of the screen to complete the first and second slurry depositions on the substrate to be printed, including:

[0138] The doctor blade 9 of the first processing head assembly and the doctor blade 11 of the third processing head assembly are lowered to contact the screen surface; the printing device is controlled to move from the first side to the second side of the screen, the first slurry deposition is completed by the doctor blade 11 of the third processing head assembly, and the second slurry deposition is completed by the doctor blade 9 of the first processing head assembly, with the second slurry deposition at least partially stacked on the first slurry deposition.

[0139] In the sixth preferred example, such as Figure 13 As shown, after completing the first and second slurry depositions, the process also includes:

[0140] The scraper 9 of the first processing head assembly and the scraper 11 of the third processing head assembly rise and do not contact the surface of the stencil, while the ink knife 24 of the second processing head assembly and the ink knife 25 of the fourth processing head assembly descend.

[0141] The printing device is controlled to move from the second side of the screen to the first side, and the ink blade 24 of the second processing head assembly and the ink blade 25 of the fourth processing head assembly are used to complete the coating of the paste.

[0142] In this solution, compared to the fifth embodiment, two consecutive slurry depositions can be completed on the same substrate surface in one printing operation. During the slurry coating process, the printed substrate is transferred out of the printing station, and optionally, it can be transferred to another substrate to be printed, which is more efficient.

[0143] In the sixth preferred embodiment, preferably, 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.

[0144] In the sixth preferred embodiment, 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.

[0145] In the sixth preferred embodiment, 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.

[0146] In the sixth preferred embodiment, preferably, the force exerted by the scraper of the third processing head assembly on the screen plate during the first slurry deposition is less than the force exerted by the scraper of the first processing head assembly on the screen plate during the second slurry deposition.

[0147] In the sixth preferred embodiment, 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; and in the second slurry deposition, the angle between the scraper of the first processing head assembly and the screen is 30 to 90 degrees.

[0148] In the above-described various embodiments and preferred examples, printing can be completed by depositing paste twice consecutively on the same substrate surface at the same work station using the same screen.

[0149] In the above embodiments and preferred examples, the screen can be a silk screen or a metal screen, preferably a metal screen. This allows for at least two continuous slurry depositions on the same substrate surface at the same workstation using the same screen, thus completing the printing process. It also eliminates the need for the existing technology of drying the slurry after the first printing and then performing the second printing, which is complex and requires alignment during the second printing, increasing the difficulty of the process.

[0150] Specifically, the metal mesh is a steel mesh. For example, openings can be formed on a metal plate using laser cutting. Compared to screen printing, the opening width of a steel mesh is between 5-15 micrometers, or even smaller. During the metal mesh printing process, the paste passes through the openings, resulting in more uniform deposition of the first and second pastes. Consequently, the grid lines formed by the stacking of the first and second deposited pastes are narrower and taller, resulting in a higher aspect ratio of the printed grid lines. This improves the conductivity of the battery and thus enhances the overall battery efficiency. Furthermore, the printing method of this invention also improves the printing efficiency of battery cells and increases production capacity.

[0151] This embodiment also provides a printing apparatus that performs the aforementioned method of printing on a substrate screen, thereby improving work efficiency and enhancing printing results.

[0152] This embodiment also provides a solar cell, which is fabricated using the aforementioned method of on-substrate screen printing. This embodiment also provides a solar cell module, which is fabricated using multiple of the aforementioned solar cells. When the grid lines of a solar cell or solar cell module are fabricated using the printing methods of the above embodiments or preferred embodiments, grid lines with a high aspect ratio can be obtained, improving the cell conversion efficiency.

[0153] Table 1

[0154]

[0155] Using the method described in the fourth preferred example above, grid lines are printed on a silicon-based solar cell with a transparent conductive layer formed thereon. The stencil is a steel mesh. Both the squeegee of the first processing head assembly and the squeegee of the second processing head assembly are steel squeegees. The grid lines produced by the above method were sampled at six different locations, and the data are shown in Table 1.

[0156] The silicon-based solar cells prepared by the above method were subjected to electrochemical efficiency (ETA) testing. The measured ETA was 26.2%.

[0157] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art will recognize that the specific embodiments described above are merely illustrative and not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art under the guidance of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for printing on a substrate screen for printing solar cells, comprising: The substrate to be printed is transferred to the printing station; Move the screen to the predetermined printing position, with the screen above the substrate to be printed and the paste on the screen. The printing device is controlled to move on the screen, and the paste is deposited twice on the same substrate to complete the printing process. The control of the printing device on the screen includes: The printing apparatus is controlled to move from the first side of the screen 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 the second deposited paste is at least partially stacked on the first deposited paste. The printing apparatus includes a first processing head assembly, a second processing head assembly, a third processing head assembly, and a fourth processing head assembly, each equipped with a doctor blade. The controlled printing device moves from the first side of the screen to the second side opposite to the first side to complete the first and second slurry depositions, including: The scrapers of the first and third processing head assemblies descend and come into contact with the surface of the stencil; the scrapers of the second and fourth processing head assemblies do not come into contact with the surface of the stencil. The printing device is controlled to move from the first side of the screen to the second side opposite to the first side, and the first slurry deposition is completed by the doctor blade of the third processing head assembly, and the second slurry deposition is completed by the doctor blade of the first processing head assembly. The amount of paste deposited onto the substrate by the scraper movement of the third processing head assembly is less than the amount of paste deposited onto the substrate by the scraper movement of the first processing head assembly. The first processing head assembly, the second processing head assembly, the third processing head assembly, and the fourth processing head assembly are arranged sequentially along the moving direction of the printing device; The force exerted by the scraper of the third processing head assembly on the screen plate during the first slurry deposition is less than the force exerted by the scraper of the first processing head assembly on the screen plate during the second slurry deposition. After printing is complete, replace the substrate with another one to be printed on; The printing device is controlled to move from the second side of the screen to the first side to complete the first and second slurry deposition on another substrate to be printed; The controlled printing device moves from the second side of the screen to the first side to complete the first and second slurry depositions on another substrate to be printed, including: The scrapers of the first and third processing head assemblies are raised so that they do not contact the surface of the stencil; the scrapers of the second and fourth processing head assemblies are lowered so that they contact the surface of the stencil. The printing device is controlled to move from the second side of the screen to the first side, and the first slurry deposition is completed by the doctor blade of the second processing head assembly, and the second slurry deposition is completed by the doctor blade of the fourth processing head assembly.

2. The method according to claim 1, wherein, The amount of paste deposited onto the substrate by the doctor blade movement of the second processing head assembly is less than the amount of paste deposited onto the substrate by the doctor blade movement of the fourth processing head assembly.

3. The method according to claim 1, wherein, The scrapers of the first processing head assembly and the fourth processing head assembly are made of a first material, while the scrapers of the second processing head assembly and the third processing head assembly are made of a second material.

4. The method according to claim 3, wherein, The hardness of the second material is greater than that of the first material.

5. The method according to claim 4, wherein, The scrapers of the first processing head assembly and the fourth processing head assembly are both rubber strip scrapers; the scrapers of the second processing head assembly and the third processing head assembly are both steel scrapers.

6. The method according to claim 1, wherein, The force exerted by the scraper of the second processing head assembly on the screen plate during the first slurry deposition is less than the force exerted by the scraper of the fourth processing head assembly on the screen plate during the second slurry deposition.

7. The method according to claim 1, wherein, In the first slurry deposition, the angle between the scraper and the screen of the third processing head assembly is 30 to 90 degrees; the angle between the scraper and the screen of the second processing head assembly is 30 to 90 degrees. In the second slurry deposition, the angle between the scraper and the screen of the first processing head assembly is 30 to 90 degrees; the angle between the scraper and the screen of the fourth processing head assembly is 30 to 90 degrees.

8. The method according to claim 1, wherein, There is no heat treatment process between the two slurry deposition processes.

9. A method for printing on a substrate screen for printing solar cells, comprising: The substrate to be printed is transferred to the printing station; Move the screen to the predetermined printing position, with the screen above the substrate to be printed and the paste on the screen. The printing device is controlled to move on the screen, and the paste is deposited twice on the same substrate to complete the printing process. The control of the printing device on the screen includes: The printing apparatus is controlled to move from the first side of the screen 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 the second deposited paste is at least partially stacked on the first deposited paste. The printing apparatus includes a first processing head assembly with a doctor blade, a second processing head assembly with an ink blade, a third processing head assembly with a doctor blade, and a fourth processing head assembly with an ink blade. The first processing head assembly, the second processing head assembly, the third processing head assembly, and the fourth processing head assembly are arranged sequentially along the moving direction of the printing device; The controlled printing device moves from the first side to the second side of the screen to complete the first and second slurry depositions on the substrate to be printed, including: The scrapers of the first processing head assembly and the third processing head assembly are lowered to contact the surface of the stencil. The printing apparatus is controlled to move from the first side to the second side of the screen, and the first slurry deposition is completed by the doctor blade of the third processing head assembly, and the second slurry deposition is completed by the doctor blade of the first processing head assembly, with the second slurry deposition at least partially stacked on the first slurry deposition; The amount of paste deposited on the substrate in the first paste deposition is less than the amount of paste deposited on the substrate in the second paste deposition; This process, following the completion of the first and second slurry depositions, also includes: The scrapers of the first and third processing head assemblies rise and do not contact the stencil surface, while the ink cutters of the second and fourth processing head assemblies descend. The printing device is controlled to move from the second side of the screen to the first side, and the ink blades of the second processing head assembly and the fourth processing head assembly are used to complete the coating of the paste.

10. The method according to claim 9, wherein, There is no heat treatment process between the two slurry deposition processes.

11. A printing apparatus, wherein the printing apparatus employs the method of printing on a substrate screen as described in any one of claims 1-10.

12. A solar cell, said solar cell being prepared by means of screen printing on a substrate as described in any one of claims 1-10.

13. A solar cell module, said solar cell module being formed using a plurality of solar cells as described in claim 12.

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