Printing method and system for solar cell electrodes

Abstract

The present invention discloses a printing method and system for solar cell electrodes, and relates to the technical field of solar cell manufacturing. The printing method comprises: (1) providing a silicon wafer to be printed; (2) cooling the silicon wafer to be printed to a temperature of ≤10°C; (3) printing the silicon wafer to be printed using a printing device; (4) drying the printed silicon wafer to shape the printed electrode grid lines. The implementation of the present invention can prevent the width and height of the printed electrode grid lines from changing significantly, and avoid the problems of increased shading area and decreased conversion efficiency caused by the widening of the electrode grid lines.

Description

Technical Field

[0001] The present invention relates to the field of solar cell manufacturing, and in particular to a printing method and system for solar cell electrodes. Background Art

[0002] At present, the electrodes of solar cells are generally prepared by screen printing. Specifically, the screen printing device mainly includes a machine, a screen, a scraper, etc. During printing, the slurry is first placed on the screen, and then the slurry on the screen is scraped out from the mesh of the screen to the silicon wafer to be printed by a scraper. Since the width of the mesh is very small (the width of the traditional sub-grid is only about 10μm, and the width of the mesh is also about 10μm), in order to ensure smooth printing, it is necessary to ensure that the slurry has good fluidity. However, this also causes the slurry printed on the surface of the silicon wafer to slide and expand to both sides of the electrode grid line, thereby increasing the width of the electrode grid line and reducing the height of the electrode grid line, which greatly increases the shading area of ​​the electrode grid line, reduces the short-circuit current, and reduces the conversion efficiency of the solar cell. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for printing solar cell electrodes, wherein after printing, the width of the electrode grid lines changes little, the shading area is small, and the conversion efficiency of the solar cell is improved.

[0004] Another technical problem to be solved by the present invention is to provide a printing system for solar cell electrodes.

[0005] Another technical problem to be solved by the present invention is to provide application of the above phosphorus diffusion method in the preparation process of SE solar cells.

[0006] In order to solve the above technical problems, the present invention provides a printing method for solar cell electrodes, which comprises:

[0007] (1) Providing a silicon wafer to be printed;

[0008] (2) cooling the silicon wafer to be printed to a temperature ≤ 10° C.;

[0009] (3) Printing the silicon wafer to be printed using a printing device;

[0010] (4) Drying the printed silicon wafer to finalize the printed electrode grid lines.

[0011] As an improvement of the above technical solution, step (3) includes:

[0012] (3.1) Printing the silicon wafer to be printed using a printing device;

[0013] (3.2) Cool the printed silicon wafer to a temperature ≤10°C.

[0014] As an improvement of the above technical solution, the printing device includes a screen, a scraper and a screen thermostat, and the screen thermostat is used to maintain a preset temperature of the screen before and after printing.

[0015] As an improvement of the above technical solution, in step (3), the scraper is used to squeeze the screen onto the silicon wafer to be printed, so that the slurry on the screen is printed onto the silicon wafer to be printed;

[0016] During the printing process, the tension of the screen and the movement speed of the scraper are controlled so that the temperature change of the screen before and after printing is ≤9°C.

[0017] As an improvement of the above technical solution, in step (2), the temperature of the silicon wafer to be printed after cooling is 5 to 8°C;

[0018] The temperature of the screen before and after printing is 20-25°C.

[0019] As an improvement of the above technical solution, in step (1), a silicon wafer to be printed is provided, and the device to be printed is loaded onto a first transmission device;

[0020] In step (2), the first transmission device is used to transmit the silicon wafer to be printed, and the first cooling device disposed on the first transmission device is used to cool the silicon wafer to be printed to a temperature of ≤10°C.

[0021] As an improvement of the above technical solution, the first cooling device is a plurality of air cooling devices, which are arranged above the first transmission device;

[0022] In step (2), the plurality of air cooling devices perform gradient cooling on the silicon wafer to be printed.

[0023] As an improvement of the above technical solution, in step (3.2), the printed silicon wafer is loaded onto a second transmission device for transmission, and a second cooling device is provided on the second transmission device to cool the printed silicon wafer.

[0024] As an improvement of the above technical solution, the second cooling device is an air cooling device, and the width of the air outlet of the air cooling device is ≤ the width between adjacent electrode grid lines;

[0025] In step (3.2), a second cooling device is used to cool the position between adjacent electrode grid lines of the printed silicon wafer.

[0026] Correspondingly, the present invention also discloses a printing system for solar cell electrodes, which is used for printing on a silicon wafer to be printed, and comprises:

[0027] A silicon wafer to be printed is provided by a unit;

[0028] A cooling unit, used to cool the silicon wafer to be printed to a temperature of ≤10°C;

[0029] Printing equipment; and

[0030] The drying unit is used to dry the printed silicon wafer to finalize the electrode grid lines obtained by printing.

[0031] The implementation of the present invention has the following beneficial effects:

[0032] 1. The printing method of the solar cell electrode of the present invention reduces the temperature of the silicon wafer to be printed to below 10°C before printing, so that the slurry is quickly cooled down after being printed on the surface of the silicon wafer, preventing the width and height of the printed electrode grid lines from changing significantly, thereby avoiding the problem of increased shading area and decreased conversion efficiency due to wider electrode grid lines.

[0033] 2. The printing method of the solar cell electrode of the present invention is provided with a screen thermostat in the printing device, so that the screen temperature before and after printing is maintained at 20-25°C, thereby maintaining the reasonable fluidity of the slurry on the screen and ensuring the printability of the slurry. Furthermore, by controlling the tension of the screen and the movement speed of the scraper, the temperature change of the screen during the printing process can be controlled to within 9°C, making the screen thermostat control of the screen temperature more accurate and easy.

[0034] 3. The printing method of the solar cell electrode of the present invention cools the silicon wafer through a highly convergent air outlet (width ≤ the width of the adjacent electrode grid lines) after printing. Firstly, the cooling effect is enhanced to reduce the flow of the electrode grid line slurry; secondly, by adjusting the blowing direction, the electrode grid lines can be squeezed by the wind from bottom to top and from both sides to the middle, thereby achieving the effect of shaping the electrode grid lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic diagram of a printing system in one embodiment of the present invention;

[0036] Figure 2 It is a schematic diagram of the working principle of the second cooling device in one embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. It is hereby stated that the directional terms such as up, down, left, right, front, back, inside, outside, etc. that appear or will appear in the text of the present invention are only based on the accompanying drawings of the present invention, and are not specific limitations of the present invention.

[0038] The present invention provides a method for printing a solar cell electrode, which comprises the following steps:

[0039] (1) Providing a silicon wafer to be printed;

[0040] (2) Cooling the silicon wafer to be printed to a temperature ≤ 10°C;

[0041] Specifically, in one embodiment of the present invention, the silicon wafer to be printed can be loaded onto a transmission device for transmission, and a cooling device disposed on the transmission device is used to cool the silicon wafer to be printed. In another embodiment of the present invention, the silicon wafer to be printed can be loaded onto a printing machine table of a printing device, and then a cooling device (liquid cooling, air cooling, but not limited thereto) is used to cool the silicon wafer to be printed.

[0042] Preferably, the silicon wafer to be printed is loaded onto the first transmission device, and the silicon wafer to be printed is cooled by a first cooling device disposed on the first transmission device. The first transmission device may be a belt conveyor or a roller conveyor, but is not limited thereto. The first cooling device may be an air cooling device or a liquid cooling device, but is not limited thereto. Preferably, the first transmission device is a belt conveyor, the first cooling device is an air cooling device, and the first cooling device is disposed above the first transmission device.

[0043] Specifically, the silicon wafer to be printed is gradually cooled by multiple air cooling devices to prevent the silicon wafer to be printed from causing hidden cracks or even ruptures due to excessive temperature changes. Preferably, the cooling rate of the silicon wafer to be printed is controlled to be 80-150°C / min. The temperature of the silicon wafer to be printed after cooling is ≤10°C. If the temperature is greater than 10°C, it is difficult to effectively reduce the flow of the slurry after printing. Preferably, the temperature of the silicon wafer to be printed after cooling is 5-8°C. When the temperature after cooling is less than 5°C, it is easy to cause the silicon wafer to become brittle, which in turn causes hidden cracks or even ruptures in the silicon wafer during printing.

[0044] (3) Printing the silicon wafer to be printed using a printing device;

[0045] Among them, the printing device can be a screen printing device, but is not limited to this. Preferably, in one embodiment of the present invention, a screen printing device is used for printing. The screen printing device includes a screen, a scraper and a screen thermostat. The screen thermostat is used to maintain the temperature of the screen before and after printing at a specific temperature (20-25°C), thereby maintaining the slurry on the screen with reasonable fluidity to ensure printability. Specifically, the screen thermostat can be a hot air device or a liquid heating device, but is not limited to this. Preferably, a hot air device is used, which has a simple structure and can cover the entire screen, so that the temperature of the entire screen is uniform.

[0046] Furthermore, during the printing process, a scraper is used to squeeze the screen onto the silicon wafer to be printed, so as to print the slurry on the screen onto the silicon wafer to be printed; during the printing process, the tension of the screen and the movement speed of the scraper are controlled, thereby effectively controlling the contact time between the screen and the silicon wafer, and thus controlling the temperature change of the screen during the printing process. Specifically, the temperature change is controlled to be ≤9°C, which reduces the control difficulty of the screen thermostat, makes the screen temperature more stable and uniform, and improves the quality of screen printing.

[0047] Preferably, in one embodiment of the present invention, step (3) comprises:

[0048] (3.1) Printing the silicon wafer to be printed using a printing device;

[0049] (3.2) Cool the printed silicon wafer to a temperature ≤10°C.

[0050] Specifically, in one embodiment of the present invention, the printed silicon wafer can be loaded onto a transmission device for transmission, and the printed silicon wafer can be cooled by a cooling device disposed on the transmission device. In another embodiment of the present invention, the printed silicon wafer can be cooled directly on a printing machine table of a printing device, but is not limited thereto.

[0051] Preferably, the printed silicon wafer is loaded onto a second conveying device, and a second cooling device disposed on the second conveying device is used to cool the printed silicon wafer. The second conveying device may be a belt conveyor or a roller conveyor, but is not limited thereto. The second cooling device may be an air cooling device or a liquid cooling device, but is not limited thereto. Preferably, the second conveying device is a belt conveyor, and the second cooling device is an air cooling device. The second cooling device is disposed above the second conveying device. Through further cooling by the second cooling device, the temperature of the printed silicon wafer can also be maintained below 10°C, further reducing the flow collapse of the electrode grid line slurry.

[0052] Specifically, the second cooling device can be arranged above or below the belt conveyor, but is not limited thereto. Specifically, in one embodiment, the second cooling device is arranged below the belt conveyor to prevent the printed slurry from being blown away.

[0053] Further preferably, in one embodiment of the present invention, a second cooling device is disposed above the second transmission device, and the second cooling device is an air cooling device, and the width of the air outlet of the air cooling device is ≤ the width between adjacent electrode grid lines; and the second cooling device is used to cool the position between adjacent electrode grid lines of the printed silicon wafer. Specifically, the width of the air outlet of the air cooling device is 0.5 to 0.8 times the width of the adjacent electrode grid lines. And the air outlet direction of the air outlet is perpendicular to the silicon wafer. Based on this arrangement, the electrode grid lines can be squeezed by wind from bottom to top and from both sides to the middle, thereby achieving the effect of shaping the electrode grid lines ( Figure 2 ).

[0054] (4) Drying the printed silicon wafer to finalize the printed electrode grid lines.

[0055] Correspondingly, the present invention also discloses a printing system for solar cell electrodes, which is used for printing on silicon wafers to be printed. Specifically, the printing system includes a unit for providing silicon wafers to be printed; a cooling unit 1, which is used to cool the silicon wafers to be printed to a temperature of ≤10°C; a printing device 2; and a drying unit 3, which is used to dry the printed silicon wafers to shape the electrode grid lines obtained by printing.

[0056] Specifically, refer to Figure 1 In one embodiment of the present invention, the cooling unit includes a first transmission device 11 and a first cooling device 12; the first transmission device 11 is a belt conveyor, but not limited thereto. The first cooling device 12 is an air cooling device, but not limited thereto.

[0057] Specifically, the printing device 2 includes a screen 21, a scraper 22 and a screen thermostat 23. The scraper 22 and the screen thermostat 23 are arranged above the screen 21. The screen thermostat 23 is a hot air device, but is not limited thereto.

[0058] Preferably, in one embodiment of the present invention, the printing system further includes a second transmission device 4 and a second cooling device 5 disposed between the printing device 2 and the drying unit 3, and the second cooling device 5 is disposed above the second transmission device 4. Specifically, the second transmission device 4 is a belt conveyor, but is not limited thereto. The second cooling device 5 is an air cooling device, but is not limited thereto.

[0059] The present invention is further described below with specific embodiments:

[0060] Example 1

[0061] This embodiment provides a method for printing solar cell electrodes, comprising the following steps:

[0062] (1) Providing a silicon wafer to be printed;

[0063] Specifically, the silicon wafer to be printed is a silicon wafer that has been heavily SE-doped on the front side and laser back-grooved (PECR);

[0064] (2) Loading the silicon wafer to be printed onto the belt and cooling it to a temperature of 2 to 3°C using an air cooling device, with the cooling rate controlled at 120°C / min;

[0065] (3) Printing was performed using a screen printing device, and the temperature of the screen before and after printing was maintained at 22-23°C by a hot air device; in addition, the screen tension was controlled to be 25N, the movement speed of the scraper was 42cm / s, the screen temperature was reduced by 11°C before and after printing, and the temperature of the silicon wafer after printing was 9.5°C;

[0066] (4) Drying and shaping the printed silicon wafer.

[0067] Example 2

[0068] This embodiment provides a method for printing solar cell electrodes, comprising the following steps:

[0069] (1) Providing a silicon wafer to be printed;

[0070] Specifically, the silicon wafer to be printed is a silicon wafer that has been heavily SE-doped on the front side and laser back-grooved (PECR);

[0071] (2) Loading the silicon wafer to be printed onto the belt and cooling it to a temperature of 8 to 8.5°C using an air cooling device, with the cooling rate controlled at 100°C / min;

[0072] (3) Printing was performed using a screen printing device, and the temperature of the screen before and after printing was maintained at 22-23°C by a hot air device; in addition, the screen tension was controlled to be 25N, the movement speed of the scraper was 42cm / s, the screen temperature was reduced by 8°C before and after printing, and the temperature of the silicon wafer after printing was 12.5°C;

[0073] (4) Drying and shaping the printed silicon wafer.

[0074] Example 3

[0075] This embodiment provides a method for printing solar cell electrodes, comprising the following steps:

[0076] (1) Providing a silicon wafer to be printed;

[0077] Specifically, the silicon wafer to be printed is a silicon wafer that has been heavily SE-doped on the front side and laser back-grooved (PECR);

[0078] (2) Loading the silicon wafer to be printed onto the belt and cooling it to a temperature of 8 to 8.5°C using an air cooling device, with the cooling rate controlled at 100°C / min;

[0079] (3) Printing was performed using a screen printing device, and the temperature of the screen before and after printing was maintained at 22-23°C by a hot air device; in addition, the screen tension was controlled to be 25N, the movement speed of the scraper was 42cm / s, the screen temperature was reduced by 8°C before and after printing, and the temperature of the silicon wafer after printing was 12.5°C;

[0080] (4) Loading the printed silicon wafer onto the belt, and cooling the printed silicon wafer using an air cooling device disposed below (on the back side of) the belt to maintain its temperature at 8 to 8.5°C;

[0081] (5) Drying the printed silicon wafer to fix the shape.

[0082] Example 4

[0083] This embodiment provides a method for printing solar cell electrodes, comprising the following steps:

[0084] (1) Providing a silicon wafer to be printed;

[0085] Specifically, the silicon wafer to be printed is a silicon wafer that has been heavily SE-doped on the front side and laser back-grooved (PECR);

[0086] (2) Loading the silicon wafer to be printed onto the belt and cooling it to a temperature of 8 to 8.5°C using an air cooling device, with the cooling rate controlled at 100°C / min;

[0087] (3) Printing was performed using a screen printing device, and the temperature of the screen before and after printing was maintained at 22-23°C by a hot air device; in addition, the screen tension was controlled to be 25N, the movement speed of the scraper was 42cm / s, the screen temperature was reduced by 8°C before and after printing, and the temperature of the silicon wafer after printing was 12.5°C;

[0088] (4) Loading the printed silicon wafer onto the belt, and using an air cooling device disposed on the belt to cool the printed silicon wafer to maintain its temperature at 8 to 8.5° C.; specifically, the width of the air outlet of the air cooling device is 0.6 times the width between adjacent electrode grid lines, and the air outlet direction of the air outlet is perpendicular to the silicon wafer.

[0089] (5) Drying the printed silicon wafer to fix the shape.

[0090] Comparative Example

[0091] The traditional non-cooling process is used for direct printing.

[0092] Test example

[0093] 100 silicon wafers were printed using the printing methods of Examples 1 to 4 and the comparative example (it should be noted that the same screen and the same electrode grid line structure design were used in Examples 1 to 4 and the comparative example), and the following tests were performed:

[0094] (1) Count the breakage rate during the printing process;

[0095] (2) Count the hidden crack rate and select silicon wafers that are not broken and have no obvious cracks; test the flexural strength. If the flexural strength is ≤80% of the flexural strength of the silicon wafer before printing, it is considered as hidden cracks and the hidden crack rate is calculated.

[0096] (3) Test the average short-circuit current and conversion efficiency of 10,000 finished batteries under 5 different conditions (1000W, AM1.5, 25°C).

[0097] (4) In each experimental group and control group, 10 silicon wafers without obvious defects (poor EL, poor appearance, leakage, etc.) were selected to test the aspect ratio of the electrode grid line and take the average value. The data were all tested using a Zeta-20 model 3D microscope under a 10× eyepiece and a 50× objective lens. The specific test results are shown in the following table:

[0098] Rupture rate Hidden crack rate Aspect Ratio <![CDATA[I sc (A)]]> η(%) Example 1 0.52％ 0.02％ 41.23％ 13.781 23.27 Example 2 0.46％ 0.03％ 40.05％ 13.774 23.25 Example 3 0.48％ 0.03％ 41.73％ 13.792 23.28 Example 4 0.56％ 0.04％ 42.25％ 13.796 23.29 Comparative Example 0.44％ 0.02％ 37.96％ 13.734 23.22

[0099] It can be seen from the above embodiments and comparative examples that the printing method of the present invention can effectively improve the aspect ratio of the electrode grid lines, thereby improving the short-circuit current and conversion efficiency of the solar cell.

[0100] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A method for printing a solar cell electrode, characterized in that: include: (1) Providing a silicon wafer to be printed; (2) cooling the silicon wafer to be printed to a temperature of 5 to 8° C.; (3) Printing the silicon wafer to be printed using a printing device; (4) drying the printed silicon wafer to finalize the electrode grid lines obtained by printing; Step (3) includes: (3.1) Printing the silicon wafer to be printed using a printing device; (3.2) using a second cooling device to cool the position between adjacent electrode grid lines of the printed silicon wafer to cool the printed silicon wafer to a temperature of ≤10° C.; The second cooling device is an air cooling device, and the width of the air outlet of the air cooling device is ≤ the width between adjacent electrode grid lines.

2. The method for printing a solar cell electrode according to claim 1, wherein: The printing device comprises a screen, a scraper and a screen thermostat, and the screen thermostat is used to maintain a preset temperature of the screen before and after printing.

3. The method for printing a solar cell electrode according to claim 2, wherein: In step (3), the scraper is used to squeeze the screen onto the silicon wafer to be printed, so that the slurry on the screen is printed onto the silicon wafer to be printed; During the printing process, the tension of the screen and the movement speed of the scraper are controlled so that the temperature change of the screen before and after printing is ≤9°C.

4. The method for printing a solar cell electrode according to claim 2, wherein: The temperature of the screen before and after printing is 20-25°C.

5. The method for printing a solar cell electrode according to claim 1, wherein: In step (1), a silicon wafer to be printed is provided, and the silicon wafer to be printed is loaded onto a first transmission device; In step (2), the first transmission device is used to transmit the silicon wafer to be printed, and the first cooling device disposed on the first transmission device is used to cool the silicon wafer to be printed to a temperature of ≤10°C.

6. The method for printing a solar cell electrode according to claim 5, characterized in that: The first cooling device is a plurality of air cooling devices, which are arranged above the first transmission device; In step (2), the plurality of air cooling devices perform gradient cooling on the silicon wafer to be printed.

7. The method for printing a solar cell electrode according to claim 1, wherein: In step (3.2), the printed silicon wafer is loaded onto a second transport device for transport, and the second transport device is provided with a second cooling device to cool the printed silicon wafer.

8. A printing system for solar cell electrodes, used for printing on silicon wafers to be printed, characterized in that: include: A silicon wafer to be printed is provided by a unit; A cooling unit, used to cool the silicon wafer to be printed to a temperature of 5-8°C; Printing device; The second cooling device is used to cool the position between the adjacent electrode grid lines of the printed silicon wafer to cool the printed silicon wafer to a temperature of ≤10°C; and A drying unit is used to dry the printed silicon wafer to finalize the electrode grid lines obtained by printing; Wherein, the second cooling device is an air cooling device, and the width of the air outlet of the air cooling device is ≤ the width between adjacent electrode grid lines.

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