A method and a processing apparatus for improving contact uniformity in laser-assisted sintering

Abstract

This invention relates to the field of photovoltaic cell technology, and discloses a method and processing apparatus for improving the contact uniformity of laser-assisted sintering. The method includes: probing the main grid of a first region on the front side of the solar cell; using a first laser power to laser scan a second region on the front side of the solar cell along the fine grid direction; applying a first reverse bias voltage to the solar cell; and adjusting the resistance value of a variable resistor according to the distance between the scanning point and the probe to balance the bias voltage difference at different scanning points, thereby enabling laser-assisted sintering in the second region; probing the main grid of the second region on the front side of the solar cell; using a second laser power to laser scan the first region on the front side of the solar cell along the fine grid direction; applying a second reverse bias voltage to the solar cell; and adjusting the resistance value of the variable resistor according to the distance between the scanning point and the probe, thereby completing the laser-assisted sintering of the first region. This method can balance the bias voltage difference at different scanning points and the interface contact differences between different regions, thereby improving cell performance and efficiency.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and more specifically to a method and processing apparatus for improving the contact uniformity of laser-assisted sintering. Background Technology

[0002] Currently, laser-assisted sintering equipment has become standard equipment for TOPCON batteries. Further improving the performance of laser-assisted sintering equipment and refining the laser-assisted sintering method will help improve the photoelectric conversion efficiency of the batteries. Among the mainstream laser-assisted sintering equipment currently available (as shown in publication numbers CN117650198A and CN117790625B), such as... Figure 1-4 As shown, the back of the solar cell 1 is supported on the conductive platform 7, and the front of the solar cell 1 is pressed against the main grid 12 by the probe 4. The conductive platform 7 and the probe 4 are electrically connected to the positive and negative terminals of the external power supply 6, respectively. At the same time, the laser 2 scans along the length direction of the fine grid 13 on the front of the solar cell 1 by focusing the laser beam, so as to form a series circuit that is electrically connected in the following order: the negative terminal of the power supply 6, the probe 4, the main grid 12 on the front, and the fine grid 13 on the front (e.g., ...). Figure 3-4 As shown), the silicon substrate 11 contact corresponding to the current laser scanning point 21, and the back gate line 14 (as shown). Figure 3-4 As shown), conductive platform 7 (as shown) Figure 1-2 As shown in the diagram, the positive terminal of the power supply 6 is connected to the laser 2 and the series circuit, while the controller 3 is electrically connected to the laser 2 and the series circuit to regulate the process parameters of laser scanning and reverse bias. In this way, a large number of photogenerated carriers can be induced in the local laser scanning area of ​​the cell 1, and free carriers can be separated by applying reverse bias. This results in a high current passing through the contact interface between the grid lines (such as the main grid 12 and the fine grid 13) and the silicon substrate 11, which generates a local instantaneous high temperature at the contact interface to quickly sinter the grid lines, thereby reducing the contact resistance and thus helping to improve the photoelectric conversion efficiency of the cell 1.

[0003] To accelerate production, improve the processing efficiency of laser-assisted sintering (EL), and prevent the probe from blocking the laser when it comes into contact with the solar cell, thus avoiding EL blackening, as shown in publication number CN117650198A, EL-assisted sintering equipment typically requires a first processing station and a second processing station to form a first sintering region and a second sintering region, respectively. Furthermore, the laser and reverse bias voltage at the first and second processing stations usually have only unified setting parameters (i.e., the process parameters for the laser and reverse bias voltage at the first and second processing stations are usually consistent).

[0004] The specific processing procedure of this laser-assisted sintering equipment is as follows: Figure 1 As shown, in the first processing station, probe 4 first presses one side of the front of the battery cell 1 (e.g., Figure 1The main grid 12 of the right half of the battery cell 1 shown is reverse biased, and the controller 3 controls the laser 2 to laser scan the half of the battery cell (such as the right half of the battery cell 1) opposite to the probe 4. Figure 1 The left half of the solar cell shown is used to form a contact (e.g., a silver-silicon contact) between the grid lines (such as the main grid 12 and the fine grid 13) of the solar cell 1 and the silicon substrate 11 through laser-assisted sintering. Then, as shown... Figure 2 As shown, at the second processing station, probe 4 presses the other side of the front of the battery cell 1 (as shown). Figure 2 The main grid 12 of the left half of the battery cell 1 shown is reverse biased, and the controller 3 controls the laser 2 to laser scan the other half of the battery cell (such as...). Figure 2 The right half of the battery cell shown is used to make the grid lines of the battery cell 1 contact the silicon substrate 11 through laser-assisted sintering, thus completing the laser-assisted sintering process of the entire battery cell 1.

[0005] However, existing laser-assisted sintering technology, as shown in CN117650198A, will further generate the following defects:

[0006] During the first processing station, the solar cell has not yet formed silver-silicon contacts, so photogenerated carriers are less prone to shunting under reverse bias. However, during the second processing station, since the first processing station has already been completed, the other half of the solar cell has formed silver-silicon contacts, making it easier for photogenerated carriers to shun under reverse bias. Therefore, if the first and second processing stations use the same process parameters (such as laser parameters and reverse bias parameters), the silver-silicon contacts on the right half of the solar cell processed in the second processing station will be higher than those on the left half of the solar cell processed in the first processing station.

[0007] Moreover, the laser scanning position is usually from a point on the front of the solar cell 1 that is far away from the probe 4 (e.g., Figure 1 , 3 As shown, the current scan point 21 starts at the far left of the front of the battery cell 1, forming the following series circuit: the negative terminal of the power supply 6, the probe 4 on the right side of the battery cell 1, the main grid 12 on the front, and the entire fine grid 13 on the front (as shown). Figure 3 As shown), current scan point 21 (as shown) Figure 3 The leftmost scan point 21 shown), and the back grid line 14 (as shown) Figure 3 As shown), conductive platform 7 (as shown) Figure 1 (As shown) and the positive terminal of power supply 6. See also Figure 1 , 4 When the laser scans to the center scanning point 21 on the front of the solar cell 1, the series circuit formed is: the negative terminal of the power supply 6, the probe 4 on the right side of the solar cell 1, the main grid 12 on the front, and the half-fine grid 13 on the front (e.g., Figure 4As shown), current scan point 21 (as shown) Figure 4 The intermediate scan point 21 and the back grid line 14 shown are shown. Figure 4 As shown), conductive platform 7 (as shown) Figure 1 (as shown) and the positive terminal of power supply 6.

[0008] Clearly, the gate line resistance of the half-finished grid on the front side of the middle scanning point is less than that of the entire fine grid on the leftmost front side. In a series circuit, the lower the gate line resistance, the lower the reverse bias voltage it receives, and the greater the actual reverse bias voltage at the scanning point. Therefore, the scanning point closer to the probe has a higher actual reverse bias voltage. Consequently, due to the influence of the gate line resistance, the reverse bias voltage at scanning points closer to the probe is higher than that at scanning points farther from the probe. This difference in bias voltage at different scanning points causes variations in the size of the laser-assisted sintering contact. Therefore, both the magnitude of the reverse bias voltage and the differences in silver-silicon contact will have a significant adverse impact on the contact performance between the gate line and the silicon substrate, which will negatively affect the battery's electrical performance and the improvement of its photoelectric conversion efficiency. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and processing apparatus for improving the contact uniformity of laser-assisted sintering.

[0010] Based on this, the present invention discloses a method for improving the contact uniformity of laser-assisted sintering, comprising the following process steps:

[0011] S1. Prepare solar cells and a processing device to improve laser-assisted sintering; the solar cells include a silicon substrate, and grid lines are arranged on both the front and back sides of the silicon substrate, the grid lines including cross-connected main grids and fine grids;

[0012] The processing device includes a laser, a pressure application component, and a controller; the pressure application component includes a probe, a variable resistor, a power supply, and a conductive platform that carries the battery cell. The positive terminal of the power supply is electrically connected to the back of the battery cell via the conductive platform, and the negative terminal of the power supply is electrically connected to the front main grid via the variable resistor and the probe.

[0013] S2. The probe presses against the main grid of the first area on the front of the battery cell. The controller controls the laser to use the first laser power to scan the second area on the front of the battery cell along the fine grid direction. The controller also controls the pressure application component to apply the first reverse bias voltage to the battery cell. The variable resistor adjusts its own resistance value according to the distance between the scanning point and the probe to balance the bias voltage difference at different scanning points, so that the second area can be laser-assisted sintering.

[0014] S3. The probe presses against the main grid of the second area on the front of the cell. The controller controls the laser to use the second laser power to scan the first area on the front of the cell along the fine grid direction. The controller also controls the pressure application component to apply a second reverse bias voltage to the cell. The variable resistor adjusts its own resistance value according to the distance between the scanning point and the probe to balance the bias voltage difference at different scanning points, so that the first area can be laser-assisted sintered.

[0015] Preferably, the first laser power is less than the second laser power, and the first reverse bias voltage is less than the second reverse bias voltage.

[0016] More preferably, the laser power of the laser is 1-30W, the laser frequency is 100-2000kHz, and the laser scanning speed is 10-100m / s; the reverse bias voltage of the pressure application component is 1-25V.

[0017] More preferably, in step S2, the first laser power is 17V and the first reverse bias voltage is 24W;

[0018] In step S3, the second laser power is 18.5V and the second reverse bias voltage is 26W.

[0019] More preferably, in steps S2 and S3, the resistance value of the variable resistor is adjusted within the range of 0-10Ω;

[0020] When the scanning point is close to the probe, the resistance of the variable resistor increases; when the scanning point is far from the probe, the resistance of the variable resistor decreases, in order to balance the bias voltage difference between different scanning points.

[0021] More preferably, the resistance value of the variable resistor is adjusted within the range of 0-2Ω.

[0022] Preferably, the first region and the second region do not completely overlap, and the first region and the second region, when superimposed, cover the grid line area of ​​the battery cell.

[0023] More preferably, the first region and the second region are the left half region and the right half region of the battery cell, respectively.

[0024] The present invention also discloses a processing device for improving laser-assisted sintering, which is applied to the method for improving the contact uniformity of laser-assisted sintering described above in the present invention;

[0025] The processing device includes a laser for laser scanning the front side of the solar cell, a pressure application assembly, and a controller connecting the laser and the pressure application assembly; the pressure application assembly includes a probe for pressing against the main grid on the front side of the solar cell, a variable resistor, a power supply, and a conductive platform for carrying the solar cell, the variable resistor being electrically connected to the probe, the conductive platform being electrically connected to the back side of the solar cell, and the negative and positive terminals of the power supply being electrically connected to the variable resistor and the conductive platform, respectively.

[0026] Preferably, the conductive platform is a copper plate; the battery cell is a crystalline silicon solar cell;

[0027] The number of controllers is two, and the two controllers control the application of the first reverse bias and the second reverse bias, respectively.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] The present invention provides a method for improving the contact uniformity of laser-assisted sintering. Through the cooperation of the above steps S1-S3, it can improve the interface contact uniformity between the second region in step S2 and the first region in step S3 by optimizing the laser power parameters and reverse bias parameters of the first and second regions. It can also achieve voltage balance at different scanning points by changing the resistance value of the added variable resistor, thus balancing the bias differences at different scanning points. This can greatly improve the contact uniformity of laser-assisted sintering, thereby greatly improving the contact performance between the grid line and the silicon substrate. This can further improve the electrical performance of the battery (such as open-circuit voltage, short-circuit current, and fill factor), promote the improvement of the battery's photoelectric conversion efficiency, and further improve the compatibility window of the grid line paste. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of a laser-assisted sintering device used for laser assisted sintering of the left half of a solar cell.

[0031] Figure 2 This is a schematic diagram of the structure of a conventional laser-assisted sintering equipment for laser-assisted sintering of the right half of a solar cell.

[0032] Figure 3 The diagram shows the series circuit after omitting the conductive platform when the laser scanning point is on the left side of the front of the solar cell.

[0033] Figure 4 This is a schematic diagram of the series circuit with the conductive platform omitted when the laser scanning point is in the middle of the front of the solar cell.

[0034] Figure 5 This is a schematic diagram of a processing device for improving laser-assisted sintering in this embodiment, used for laser-assisted sintering of the left half of a battery cell.

[0035] Figure 6 This is a schematic diagram of a processing device for improving laser-assisted sintering in this embodiment, showing the structure of the right half of the battery cell being laser-assisted sintered.

[0036] Reference numerals: 1. Solar cell; 11. Silicon substrate; 12. Main grid; 13. Fine grid; 14. Back grid line;

[0037] 2. Laser; 21. Scanning point; 3. Controller; 4. Probe; 5. Variable resistor; 6. Power supply; 7. Conductive platform. Detailed Implementation

[0038] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Example 1

[0040] This embodiment provides a processing apparatus for improving laser-assisted sintering, used to optimize the laser-assisted sintering of a solar cell 1. The solar cell 1 includes a silicon substrate 11, with a plurality of grid lines arranged on both the front and back sides of the silicon substrate 11. The grid lines include cross-connected main grids 12 and fine grids 13. The solar cell 1 is preferably a crystalline silicon solar cell.

[0041] This embodiment provides an improved processing apparatus for laser-assisted sintering, see [link to relevant documentation]. Figure 5-6 The system includes a laser 2, a pressure application component, and a controller 3. The laser 2 is used to laser scan the front side of the solar cell 1; the pressure application component is used to apply a reverse bias voltage to the solar cell 1. In this way, laser-assisted sintering of the solar cell 1 is achieved through laser scanning and the application of the reverse bias voltage.

[0042] Both the laser 2 and the pressure application component are connected to the controller 3, so that the controller 3 can adjust the process parameters of the laser scanning of the laser 2 (such as laser power, laser frequency, laser scanning speed, etc.), and also adjust the magnitude of the reverse bias voltage applied by the pressure application component.

[0043] The pressure-applying assembly includes a probe 4, a variable resistor 5, a power supply 6, and a conductive platform 7 supporting the battery cell 1. The conductive platform 7 is mounted on the back of the battery cell 1, electrically connecting it to the main grids 12 on the back of the battery cell 1. One end of the probe 4 presses against the main grids 12 on the front of the battery cell 1, while the other end of the probe 4 is electrically connected to the variable resistor 5. The negative terminal of the power supply 6 is electrically connected to the variable resistor 5, and the positive terminal of the power supply 6 is electrically connected to the conductive platform 7. Therefore, the positive terminal of the power supply 6 is electrically connected to the main grids 12 on the back of the battery cell 1 via the conductive platform 7, while the negative terminal of the power supply 6 is electrically connected to the left or right main grids 12 on the front of the battery cell via the variable resistor 5 and the probe 4; thus, a reverse bias voltage can be applied to the battery cell 1 for laser-assisted sintering. The conductive platform 7 is preferably a copper plate.

[0044] In practice, there can be only one controller 3. In this case, the controller 3 controls both the laser scanning and reverse bias process parameters for laser-assisted sintering in the second region (i.e., the left half region) of the battery cell 1, and the laser scanning and reverse bias process parameters for laser-assisted sintering in the first region (i.e., the right half region) of the battery cell 1.

[0045] In this embodiment, the number of controllers 3 is preferably two, and correspondingly, the number of variable resistors 5 and probes 4 is also two. The two probes 4 press against the main grid 12 of the first region and the main grid 12 of the second region on the front side of the battery cell 1, respectively, and the two variable resistors 5 are electrically connected to the two probes 4. To reduce equipment investment costs, the laser-assisted sintering of the second region and the first region share the same laser 2, power supply 6, and conductive platform 7. At this time, one controller 3 is used to control the laser scanning and reverse bias process parameters (such as the first reverse bias and the first laser power) of the laser-assisted sintering in the second region, while the other controller 3 is used to control the laser scanning and reverse bias process parameters (such as the second laser power and the second reverse bias) of the laser-assisted sintering in the first region.

[0046] The processing device for improving laser-assisted sintering described above in this embodiment is applied to a method for improving the contact uniformity of laser-assisted sintering as described below in this embodiment.

[0047] This embodiment of a method for improving the contact uniformity of laser-assisted sintering includes the following process steps:

[0048] S1. Prepare the battery cell 1 and the processing device for improving laser-assisted sintering.

[0049] S2, see also Figure 5 The probe 4 first presses down on the main grid 12 of the first region on the front of the solar cell 1; the controller 3 controls the laser 2 to focus the laser beam using the first laser power and begin to scan the second region (i.e., the left half region) on the front of the solar cell 1 along the direction of the fine grid 13 to induce the formation of a large number of photogenerated carriers; the controller 3 also controls the pressure application component to apply a first reverse bias voltage to the solar cell 1; and the variable resistor 5 adjusts its own resistance value according to the distance between the scanning point 21 and the probe 4 to balance the bias voltage difference borne by different scanning points 21. At this time, a large number of photogenerated carriers will cause a high current to pass through the contact interface between the silicon substrate 11 and the grid line, forming a local instantaneous high temperature to quickly sinter the grid line in the second region, thus realizing the laser-assisted sintering of the second region.

[0050] S3, see also Figure 6The probe 4 then presses against the main grid 12 of the second region on the front of the solar cell 1. The controller 3 controls the laser 2 to focus the laser beam using the second laser power and begin laser scanning the first region (i.e., the right half region) on the front of the solar cell 1 along the direction of the fine grid 13 to induce the formation of a large number of photogenerated carriers. The controller 3 also controls the pressure application component to apply a second reverse bias voltage to the solar cell 1. Furthermore, the variable resistor 5 adjusts its resistance value according to the distance between the scanning point 21 and the probe 4 to balance the bias voltage differences experienced by different scanning points 21. Therefore, a large number of photogenerated carriers cause a high current to flow through the contact interface between the silicon substrate 11 and the grid lines, forming a localized instantaneous high temperature to rapidly sinter the grid lines in the first region, thus achieving laser-assisted sintering of the first region. After completing the laser-assisted sintering of the first region, the probe 4 is removed, ending the laser-assisted sintering process.

[0051] The first region and the second region do not completely overlap, and the superposition of the first region and the second region covers the entire grid line area of ​​the battery cell 1. Preferably, the first region and the second region are the left half region and the right half region of the battery cell 1, respectively.

[0052] Among them, the laser power of laser 2 is 1-30W, the laser frequency is 100-2000kHz, and the laser scanning speed is 10-100m / s; the reverse bias voltage of the pressure application component is 1-25V.

[0053] To effectively avoid the following problem existing in the prior art such as CN117650198A: "Because during the second processing station, the silver-silicon contact formed on the right half of the solar cell 1 can easily cause photogenerated carriers to be shunted under reverse bias, if the first and second processing stations use the same process parameters, the silver-silicon contact on the right half of the solar cell 1 processed in the second processing station will be higher than that on the left half of the solar cell 1 processed in the first processing station." In steps S2 and S3 of this embodiment, the first laser power is less than the second laser power, and the first reverse bias is less than the second reverse bias; thus, the difference in interface contact (such as the silver-silicon contact between the silicon substrate 11 and the gate line) between the second region (corresponding to the right half of the solar cell 1) in step S2 and the first region (corresponding to the left half of the solar cell 1) in step S3 can be balanced.

[0054] Preferably, in step S2, the first laser power is 17V and the first reverse bias voltage is 24W; in step S3, the second laser power is 18.5V and the second reverse bias voltage is 26W.

[0055] In practice, the parameter values ​​for laser frequency and laser scanning speed in step S2 are the same as those in step S3. For example, the laser frequency in both steps S2 and S3 is 800kHz, and the laser scanning speed is 50m / s.

[0056] Furthermore, to effectively avoid the following problem existing in the prior art such as CN117650198A, "due to the influence of the gate line resistance, the reverse bias voltage of the scanning point 21 near the probe 4 is higher than that of the scanning point 21 far from the probe 4," this embodiment adds a variable resistor 5 to the pressure application assembly. This variable resistor 5 can sense the distance between the laser scanning fine gate 13 position (i.e., scanning point 21) and the probe 4, and then automatically adjust its resistance value according to this distance. This variable resistor 5 is an existing device; for example, the model of the variable resistor 5 can be the PRS-370 self-adjusting programmable resistor device from IETLAS.A.

[0057] In practice, the range of resistance value variation of the variable resistor 5 can be set with reference to the previously measured grid line resistance data. Specifically, in steps S2 and S3, the resistance value adjustment range of the variable resistor 5 is controlled within 0-10Ω, preferably 0-2Ω.

[0058] The resistance value of the variable resistor 5 can be automatically adjusted according to the distance between the laser scanning point 21 and the probe 4, specifically as follows: when the scanning point 21 is close to the probe 4, the distance between the scanning point 21 and the probe 4 is small, which will form a... Figure 4 The following series circuit is shown: negative terminal of power supply 6, probe 4 to the right of battery cell 1, main grid 12 on the front, half of the fine grid 13 on the front, and current scan point 21 (e.g., Figure 4 The intermediate scan point 21, the back grid line 14, the conductive platform 7, and the positive terminal of the power supply 6 are shown. At this time, the grid line resistance is small, and the reverse bias voltage distributed by the grid line resistance is small. Therefore, the resistance value of the variable resistor 5 needs to be increased. Conversely, when the scan point 21 is far away from the probe 4, the reverse bias voltage distributed by the grid line resistance is large. At this time, the resistance value of the variable resistor 5 needs to be decreased. In this way, the bias voltage difference of different scan points 21 can be balanced.

[0059] In summary, the method for improving the contact uniformity of laser-assisted sintering in this embodiment, through the cooperation of the above steps S1-S3, can balance the interface contact difference between the second region (corresponding to the right half of the cell 1) in step S2 and the first region (corresponding to the left half of the cell 1) in step S3 by optimizing the laser power parameters and reverse bias parameters of the first and second regions. It can also achieve voltage balance of different scanning points 21 by changing the resistance value of the added variable resistor 5. Therefore, it can balance the bias difference of different scanning points 21, greatly improve the contact uniformity of laser-assisted sintering, thereby greatly improving the contact performance between the grid line and the silicon substrate 11, thereby improving the electrical performance of the cell (such as open circuit voltage, short circuit current, fill factor), promoting the improvement of the photoelectric conversion efficiency of the cell, and further improving the adaptation window of the grid line paste.

[0060] Comparative Example 1

[0061] This comparative example of a laser-assisted sintering device and a laser-assisted sintering method both refer to Example 1, but differs from Example 1 in that:

[0062] This comparative example is a laser-assisted sintering device; see [link to example]. Figure 1-2 The laser-assisted sintering of its second and first regions both share the same controller; and the pressure application component in this comparative example omits the variable resistor.

[0063] In this comparative example, a laser-assisted sintering method omits the process of the variable resistor adjusting its resistance value based on the distance between the scanning point and the probe in steps S2 and S3; the first laser power and the second laser power are the same, both 25W; the first reverse bias voltage and the second reverse bias voltage are also the same, both 17V.

[0064] Performance testing

[0065] 1. The contact resistivity distribution data of different positions of the battery cell after being treated by the existing laser-assisted sintering method of Comparative Example 1 are shown in Table 1 below.

[0066] Table 1

[0067]

[0068]

[0069] As shown in Table 1, the contact resistivity of the battery cell treated by the existing laser-assisted sintering method of Comparative Example 1 is high on the left half and low on the right half. In other words, the contact resistivity of the battery cell treated by Comparative Example 1 is obviously unevenly distributed at different locations.

[0070] 2. The contact resistivity distribution data of different positions of the battery cell after being treated by the method of improving the contact uniformity of laser-assisted sintering in Example 1 are shown in Table 2 below.

[0071] Table 2

[0072]

[0073]

[0074] As shown in Table 2, the contact resistivity difference between the left and right halves of the solar cell treated using the method for improving laser-assisted sintering contact uniformity in Example 1 is not significant. Therefore, compared with Comparative Example 1, the contact resistivity uniformity at different locations of the solar cell treated in Example 1 is significantly improved.

[0075] 3. Performance tests were conducted on the treated solar cells of Comparative Example 1 and Example 1, and the test data are shown in Table 3 below. In Table 3, Eta is the photoelectric conversion efficiency of the cell, Uoc is the open-circuit voltage, Isc is the short-circuit current, and FF is the fill factor.

[0076] Table 3

[0077]

[0078] As shown in Table 3, compared with Comparative Example 1, the solar cell treated with the method of improving the contact uniformity of laser-assisted sintering in Example 1 has improved photoelectric conversion efficiency, open-circuit voltage, short-circuit current and fill factor.

[0079] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0080] The technical solution provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for improving the contact uniformity in laser-assisted sintering, characterized in that, The process includes the following steps: S1. Prepare solar cells and a processing device to improve laser-assisted sintering; the solar cells include a silicon substrate, and grid lines are arranged on both the front and back sides of the silicon substrate, the grid lines including cross-connected main grids and fine grids; The processing device includes a laser, a pressure application component, and a controller; the pressure application component includes a probe, a variable resistor, a power supply, and a conductive platform that carries the battery cell. The positive terminal of the power supply is electrically connected to the back of the battery cell via the conductive platform, and the negative terminal of the power supply is electrically connected to the front main grid via the variable resistor and the probe. S2. The probe presses against the main grid of the first area on the front of the battery cell. The controller controls the laser to use the first laser power to scan the second area on the front of the battery cell along the fine grid direction. The controller also controls the pressure application component to apply the first reverse bias voltage to the battery cell. The variable resistor adjusts its own resistance value according to the distance between the scanning point and the probe to balance the bias voltage difference at different scanning points, so that the second area can be laser-assisted sintering. S3. The probe presses against the main grid of the second area on the front of the battery cell. The controller controls the laser to use the second laser power to scan the first area on the front of the battery cell along the fine grid direction. The controller also controls the pressure application component to apply a second reverse bias voltage to the battery cell. The variable resistor adjusts its own resistance value according to the distance between the scanning point and the probe to balance the bias voltage difference at different scanning points, so that the first area can be laser-assisted sintering. The first laser power is less than the second laser power, and the first reverse bias voltage is less than the second reverse bias voltage.

2. The method of claim 1, wherein, The laser has a laser power of 1-30W, a laser frequency of 100-2000kHz, and a laser scanning speed of 10-100m / s; the reverse bias voltage of the pressure application component is 1-25V.

3. The method for improving contact uniformity in laser-assisted sintering according to claim 2, characterized in that, In step S2, the first laser power is 17V and the first reverse bias voltage is 24W. In step S3, the second laser power is 18.5V and the second reverse bias voltage is 26W.

4. The method of claim 1, wherein, In steps S2 and S3, the resistance value of the variable resistor is adjusted within the range of 0-10Ω; When the scanning point is close to the probe, the resistance of the variable resistor increases; when the scanning point is far from the probe, the resistance of the variable resistor decreases, in order to balance the bias voltage difference between different scanning points.

5. The method for improving contact uniformity in laser-assisted sintering according to claim 4, characterized in that, The resistance value of the variable resistor is adjustable within the range of 0-2Ω.

6. The method of claim 1, wherein, The first region and the second region do not completely overlap, and the first region and the second region, when superimposed, cover the grid line area of ​​the battery cell.

7. The method for improving contact uniformity in laser-assisted sintering according to claim 6, characterized in that, The first region and the second region are the left and right halves of the battery cell, respectively.

8. A processing apparatus for improving laser-assisted sintering, characterized by, Applied to the method for improving contact uniformity in laser-assisted sintering as described in any one of claims 1-7; The processing device includes a laser for laser scanning the front side of the solar cell, a pressure application assembly, and a controller connecting the laser and the pressure application assembly; the pressure application assembly includes a probe for pressing against the main grid on the front side of the solar cell, a variable resistor, a power supply, and a conductive platform for carrying the solar cell, the variable resistor being electrically connected to the probe, the conductive platform being electrically connected to the back side of the solar cell, and the negative and positive terminals of the power supply being electrically connected to the variable resistor and the conductive platform, respectively.

9. The apparatus for improving laser-assisted sintering of claim 8, wherein, The conductive platform is a copper plate; the battery cell is a crystalline silicon solar cell. The number of said controllers is two, each of the two controllers controlling the application of the first and second reverse bias, respectively.

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