Method and processing device for improving laser-assisted sintering contact uniformity

Abstract

The invention relates to the technical field of photovoltaic cells, and discloses a method for improving laser-assisted sintering contact uniformity and a processing device. The method comprises the steps that a probe presses a main grid of a first area on the front face of a battery piece, first laser power is used for scanning a second area on the front face of the battery piece in a laser scanning mode in the fine grid direction, first reverse bias voltage is applied to the battery piece, and a variable resistor adjusts the resistance value of the variable resistor according to the distance between scanning point positions and the probe so as to balance the bias voltage difference of different scanning point positions; performing laser-assisted sintering on the second area; the probe presses a main grid of a second area on the front face of the battery piece, laser scanning is conducted on a first area on the front face of the battery piece in the fine grid direction through second laser power, second reverse bias voltage is applied to the battery piece, the resistance value of the variable resistance piece is adjusted according to the distance between the scanning point position and the probe, and laser-assisted sintering of the first area is completed. According to the method, the bias voltage difference of different scanning point positions can be balanced, the interface contact difference of different areas can be balanced, and the battery performance and effect can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of solar cells, and in particular to a method and a processing device for improving contact uniformity of laser-assisted sintering. Background Art

[0002] At present, laser-assisted sintering equipment has become the standard configuration of TOPCON batteries. Further improving the performance of laser-assisted sintering equipment and improving the laser-assisted sintering method will help improve the photoelectric conversion efficiency of batteries. Among the current mainstream laser-assisted sintering equipment (such as those shown in publication numbers CN117650198A and CN117790625B), Figure 1-4 As shown, the back of the cell 1 is carried on the conductive platform 7, and the front of the cell 1 is pressed against the main grid 12 of the cell 1 by the probe 4. The conductive platform 7 and the probe 4 are electrically connected to the positive and negative electrodes 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 cell 1 by focusing the laser beam to form the following series circuit electrically connected in sequence: the negative electrode of the power supply 6, the probe 4, the main grid 12 on the front, and the fine grid 13 on the front (as shown in FIG. Figure 3-4 As shown), the silicon substrate 11 contact corresponding to the current laser scanning position 21, the back gate line 14 (as shown Figure 3-4 As shown), the conductive platform 7 (as Figure 1-2 As shown) and the positive electrode of the power supply 6, the controller 3 is electrically connected to the laser 2 and the series circuit to adjust the process parameters of the laser scanning and the reverse bias; in this way, a large number of photogenerated carriers can be induced to form in the local laser scanning area of ​​the battery cell 1, and the free carriers are separated by applying a reverse bias, resulting in a high current passing through the contact interface between the gate line (such as the main gate 12, the fine gate 13) and the silicon substrate 11, so that the contact interface generates a local instantaneous high temperature to quickly sinter the gate line, thereby reducing the contact resistance, which helps to improve the photoelectric conversion efficiency of the battery cell 1.

[0003] In order to speed up the production cycle, improve the processing efficiency of laser-assisted sintering, and avoid blocking the laser when the probe abuts against the battery cell, thereby avoiding the EL blackening phenomenon. As shown in publication number CN117650198A, the laser-assisted sintering equipment usually needs to set up a first processing station and a second processing station to form a first sintering area and a second sintering area respectively, and the laser and reverse bias of the first processing station and the second processing station usually have only unified setting parameters (that is, the process parameters of the laser and reverse bias of the first processing station are usually consistent with the process parameters of the laser and reverse bias of the second processing station).

[0004] The specific processing process of this laser-assisted sintering equipment is as follows: Figure 1 As shown, at the first processing station, the probe 4 first presses one side of the front side of the battery cell 1 (such as Figure 1The main grid 12 of the right half of the cell 1 shown in FIG. 1 is applied with a reverse bias, and the controller 3 controls the laser 2 to laser scan the half of the cell opposite to the probe 4 (as shown in FIG. 1 ). Figure 1 The left half of the cell is shown in the figure) so that the grid lines (such as the main grid 12 and the fine grid 13) of the cell 1 are in contact with the silicon substrate 11 through laser assisted sintering (such as forming a silver silicon contact). Then, as Figure 2 As shown, at the second processing station, the probe 4 presses the other side of the front side of the battery cell 1 (as shown in FIG. Figure 2 The main grid 12 of the left half of the cell 1 shown in FIG. 1 is applied with a reverse bias, and the controller 3 controls the laser 2 to laser scan the other half of the cell (such as Figure 2 The right half of the cell is shown in the figure), so that the gate line of the cell 1 is in contact with the silicon substrate 11 through laser assisted sintering, and thus the laser assisted sintering process of the entire cell 1 can be completed.

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

[0006] When the cell is processed at the first processing station, the silver-silicon contact has not yet been formed on the cell, so the photogenerated carriers are not easily shunted under the influence of reverse bias; while when the cell is processed at the second processing station, the silver-silicon contact has been formed on the other half of the cell because it has just been processed at the first processing station, so the photogenerated carriers are easily shunted under the influence of reverse bias. Therefore, if the same process parameters (such as laser parameters and reverse bias parameters) are used for the first processing station and the second processing station, the silver-silicon contact of the right half of the cell processed at the second processing station will be higher than that of the left half of the cell processed at the first processing station.

[0007] Moreover, the laser scanning position is usually from a point on the front side of the battery cell 1 far away from the probe 4 (such as Figure 1 , 3 As shown, the current scanning point 21 starts at the leftmost position on the front of the battery cell 1. At this time, the following series circuit will be formed: the negative electrode of the power supply 6, the probe 4 on the right side of the battery cell 1, the main grid 12 on the front side, and the entire fine grid 13 on the front side (as shown in FIG. Figure 3 As shown), the current scanning point 21 (as shown Figure 3 The leftmost scanning point 21 shown), the back grid line 14 (such as Figure 3 As shown), the conductive platform 7 (as Figure 1 As shown) and the positive terminal of the power supply 6. Figure 1 , 4 When the laser scans to the middle scanning point 21 on the front of the battery cell 1, the series circuit formed is: the negative electrode 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 half fine grid 13 on the front (such as Figure 4As shown), the current scanning point 21 (as shown Figure 4 The middle scanning point 21 shown), the back gate line 14 (such as Figure 4 As shown), the conductive platform 7 (as Figure 1 As shown) and the positive pole of the power supply 6.

[0008] Obviously, the gate line resistance of the half-thick grid on the front side of the middle scanning point is smaller than the gate line resistance of the entire thin grid on the left side. In the series circuit, the lower the gate line resistance, the lower the reverse bias voltage it receives, and the greater the actual reverse bias voltage of the scanning point; therefore, the closer the scanning point is to the probe, the higher the actual reverse bias voltage is. Therefore, due to the influence of the gate line resistance, the reverse bias voltage will cause the scanning point close to the probe to bear a higher reverse bias voltage than the scanning point far from the probe. The difference in bias voltage borne by different scanning points will cause the difference in the size of the laser-assisted sintering contact. Therefore, whether it is the size of the reverse bias voltage or the difference in silver-silicon contact, it will have a significant adverse effect on the contact performance between the gate line and the silicon substrate, which will have an adverse effect on the electrical performance of the battery and the improvement of the battery's photoelectric conversion efficiency. Summary of the invention

[0009] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method and a processing device for improving contact uniformity of laser assisted sintering.

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

[0011] S1, prepare a cell and a processing device for improving laser-assisted sintering; the cell comprises a silicon substrate, and grid lines are arranged on both the front and back sides of the silicon substrate, and the grid lines include cross-connected main grids and fine grids;

[0012] The processing device includes a laser, a pressure component and a controller; the pressure component includes a probe, a variable resistor, a power supply and a conductive platform for carrying a battery cell, the positive electrode of the power supply is electrically connected to the back of the battery cell through the conductive platform, and the negative electrode of the power supply is electrically connected to the front main grid through the variable resistor and the probe in sequence;

[0013] S2, the probe presses the main grid of the first area on the front side of the battery cell, the controller controls the laser to use the first laser power to laser scan the second area on the front side of the battery cell along the fine grid direction, and controls the pressure component to apply a first reverse bias to the battery cell, and the variable resistor adjusts its own resistance value according to the distance between the scanning point and the probe to balance the bias difference at different scanning points, so that the second area is laser-assisted sintered;

[0014] S3. The probe presses the main grid of the second area on the front side of the battery cell. The controller controls the laser to use the second laser power to laser scan the first area on the front side of the battery cell along the fine grid direction, and controls the pressure-applying component to apply a second reverse bias 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 difference at different scanning points, so that the first area can be laser-assisted sintered.

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

[0016] Further 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; and the reverse bias voltage of the pressure-applying 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] Further preferably, in steps S2 and S3, the resistance value adjustment range of the variable resistor is controlled within 0-10Ω;

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

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

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

[0023] Further preferably, the first area and the second area are respectively the left half area and the right half area of ​​the battery cell.

[0024] The present invention also discloses a processing device for improving laser-assisted sintering, which is applied to the method for improving 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 battery cell, a pressure component and a controller connecting the laser and the pressure component; the pressure component includes a probe for pressing the main grid on the front side of the battery cell, a variable resistor, a power supply and a conductive platform for supporting the battery cell, the variable resistor is electrically connected to the probe, the conductive platform is electrically connected to the back side of the battery cell, and the negative and positive electrodes of the power supply are electrically connected to the variable resistor and the conductive platform respectively.

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

[0027] There are two controllers, and the two controllers respectively control the application of the first reverse bias voltage and the second reverse bias voltage.

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

[0029] A method for improving the uniformity of laser-assisted sintering contact of the present invention, through the mutual cooperation of the above-mentioned steps S1-S3, can not only improve the uniformity of the interface contact between the second area of ​​step S2 and the first area of ​​step S3 by optimizing the laser power parameters and reverse bias parameters of the first area and the second area, but also achieve the voltage balance of different scanning points by changing the resistance value of the added variable resistor, so as to balance the bias difference of different scanning points, and can greatly improve the uniformity of laser-assisted sintering contact, thereby greatly improving the contact performance between the gate line and the silicon substrate, and further improving the electrical performance of the battery (such as open circuit voltage, short circuit current, fill factor), and can promote the improvement of the photoelectric conversion efficiency of the battery, and can further improve the adaptation window of the gate line slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the structure of laser-assisted sintering of the left half of the battery cell using existing laser-assisted sintering equipment.

[0031] Figure 2 This is a schematic diagram of the structure of laser-assisted sintering of the right half of the battery cell using existing laser-assisted sintering equipment.

[0032] Figure 3 The schematic diagram of the series circuit behind the conductive platform is omitted when the laser scanning point is located on the left side of the front side of the solar cell.

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

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

[0035] Figure 6 This is a schematic structural diagram of a processing device for improving laser-assisted sintering in this embodiment that performs laser-assisted sintering on the right half of the battery cell.

[0036] Description of the reference numerals: cell 1; silicon substrate 11; main grid 12; fine grid 13; back grid line 14;

[0037] Laser 2; scanning point 21; controller 3; probe 4; variable resistor 5; power supply 6; conductive platform 7. DETAILED DESCRIPTION

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Example 1

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

[0041] A processing device for improving laser assisted sintering in this embodiment, see Figure 5-6 , including a laser 2, a pressure component and a controller 3. The laser 2 is used to laser scan the front of the battery cell 1; the pressure component is used to apply a reverse bias to the battery cell 1. In this way, laser-assisted sintering of the battery cell 1 is achieved through laser scanning and application of a reverse bias.

[0042] Among them, the laser 2 and the pressure-applying component are both 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 the controller 3 can also adjust the reverse bias voltage applied by the pressure-applying component.

[0043] Wherein, the pressure-applying assembly includes a probe 4, a variable resistor 5, a power source 6, and a conductive platform 7 that supports the battery cell 1. The back of the battery cell 1 supports the conductive platform 7 so that the conductive platform 7 is electrically connected to each main grid 12 on the back of the battery cell 1. One end of the probe 4 presses against the main grid 12 on the front of the battery cell 1, and the other end of the probe 4 is electrically connected to the variable resistor 5. The negative pole of the power source 6 is electrically connected to the variable resistor 5, and the positive pole of the power source 6 is electrically connected to the conductive platform 7. Therefore, the positive pole of the power source 6 is electrically connected to each main grid 12 on the back of the battery cell 1 through the conductive platform 7, and the negative pole of the power source 6 is electrically connected to the main grid 12 on the left or right side of the front of the battery through the variable resistor 5 and the probe 4 in sequence; in this way, a reverse bias can be applied to the battery cell 1 for laser-assisted sintering. The conductive platform 7 is preferably a copper plate.

[0044] In practice, the number of controllers 3 may be one. In this case, the controller 3 not only regulates the laser scanning and reverse bias process parameters of the laser assisted sintering in the second area (i.e., the left half area) of the cell 1, but also regulates the laser scanning and reverse bias process parameters of the laser assisted sintering in the first area (i.e., the right half area) of the 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 are also two; the two probes 4 respectively press the main grid 12 of the first area and the main grid 12 of the second area on the front of the battery cell 1, and the two variable resistors 5 are electrically connected to the two probes 4. In order to reduce the cost of equipment investment, the laser-assisted sintering of the second area and the first area 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, the first laser power) of the laser-assisted sintering in the second area, and the other controller 3 is used to control the laser scanning and reverse bias process parameters (such as the second laser power, the second reverse bias) of the laser-assisted sintering in the first area.

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

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

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

[0049] S2, see Figure 5 , the probe 4 first presses the main grid 12 of the first area on the front of the cell 1; the controller 3 controls the laser 2 to use the first laser power to focus the laser beam and start laser scanning the second area (i.e., the left half area) on the front of the cell 1 along the direction of the fine grid 13 to induce the formation of a large number of photogenerated carriers; and the controller 3 also controls the pressure component to apply a first reverse bias to the 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 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 gate line, forming a local instantaneous high temperature to quickly sinter the gate line in the second area, so that the laser-assisted sintering of the second area can be achieved.

[0050] S3, see Figure 6, the probe 4 then presses the main grid 12 of the second area on the front side of the cell 1, and the controller 3 controls the laser 2 to use the second laser power to focus the laser beam to start laser scanning the first area (i.e., the right half area) on the front side of the cell 1 along the direction of the fine grid 13 to induce the formation of a large number of photogenerated carriers; and the controller 3 also controls the pressure-applying component to apply a second reverse bias to the 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 difference borne by different scanning points 21. Therefore, a large number of photogenerated carriers will cause a high current to pass through the contact interface between the silicon substrate 11 and the gate line, forming a local instantaneous high temperature to quickly sinter the gate line in the first area, so that the laser-assisted sintering of the first area can be achieved. After completing the laser-assisted sintering of the first area, remove the probe 4 to end the laser-assisted sintering process.

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

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

[0053] In order to effectively avoid the following problem existing in the prior art such as CN117650198A, "because the silver-silicon contact formed on the right half of the cell 1 during the second processing station processing will cause the photogenerated carriers to be easily shunted under the reverse bias, if the first processing station processing and the second processing station processing use the same process parameters, the silver-silicon contact of the right half of the cell 1 processed by the second processing station will be higher than that of the left half of the cell 1 processed by 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; in this way, the difference in interface contact (such as the silver-silicon contact between the silicon substrate 11 and the gate line) between the second area of ​​step S2 (corresponding to the right half of the cell 1) and the first area of ​​step S3 (corresponding to the left half of the cell 1) 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 ​​of the laser frequency and the laser scanning speed in step S2 are the same as the parameter values ​​of the laser frequency and the laser scanning speed in step S3. For example, the laser frequencies in steps S2 and S3 are both 800 kHz, and the laser scanning speeds are both 50 m / s.

[0056] Furthermore, in order to effectively avoid the following problem existing in the prior art of CN117650198A, "the reverse bias voltage will cause the scanning point 21 close to the probe 4 to bear a higher reverse bias voltage than the scanning point 21 far from the probe 4 due to the influence of the gate line resistance". In this embodiment, a variable resistor 5 is added to the pressure component, and the variable resistor 5 can sense the distance between the position of the fine grid 13 scanned by the laser (i.e., the scanning point 21) and the probe 4, and then the variable resistor 5 can automatically adjust its resistance value according to the distance. The variable resistor 5 is an existing device, for example, the model of the variable resistor 5 can be selected from the PRS-370 self-adjusting programmable resistor device of IETLABS Company of the United States.

[0057] In practice, the resistance value variation range of the variable resistor 5 can be set with reference to the gate line resistance data measured previously. 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 as the laser scanning point 21 is closer to the probe 4. Specifically, when the scanning point 21 is close to the probe 4, the distance between the scanning point 21 and the probe 4 is small, and the following is formed: Figure 4 The following series circuit is shown: the negative electrode of the power supply 6, the probe 4 on the right side of the battery cell 1, the main grid 12 on the front side, the half fine grid 13 on the front side, the current scanning point 21 (such as Figure 4 The middle scanning point 21 shown in the figure), the back grid line 14, the positive pole of the conductive platform 7 and the power supply 6, at this moment, the grid line resistance is small, and the reverse bias voltage allocated to the grid line resistance is small, so at this moment, it is necessary to increase the resistance value of the variable resistor 5. On the contrary, when the scanning point 21 is far away from the probe 4, the reverse bias voltage allocated to the grid line resistance is large, and at this moment, it is necessary to reduce the resistance value of the variable resistor 5. In this way, the bias difference of different scanning points 21 can be balanced.

[0059] In summary, the method of improving the uniformity of laser-assisted sintering contact in this embodiment, through the mutual cooperation of the above-mentioned steps S1-S3, can not only balance the interface contact difference between the second area of ​​step S2 (corresponding to the right half area of ​​the battery cell 1) and the first area of ​​step S3 (corresponding to the left half area of ​​the battery cell 1) by optimizing the laser power parameters and reverse bias parameters of the first area and the second area, but also achieve the voltage balance of different scanning points 21 by changing the resistance value of the added variable resistor 5, so as to balance the bias difference of different scanning points 21, greatly improve the uniformity of laser-assisted sintering contact, thereby greatly improving the contact performance between the gate line and the silicon substrate 11, and further improve the electrical performance of the battery (such as open circuit voltage, short circuit current, fill factor), and promote the improvement of the photoelectric conversion efficiency of the battery, and further improve the adaptation window of the gate line slurry.

[0060] Comparative Example 1

[0061] A laser-assisted sintering device and a laser-assisted sintering method in this comparative example are both referred to in Example 1, and the difference between them and Example 1 is that:

[0062] A laser-assisted sintering device in this comparative example, see Figure 1-2 , the laser-assisted sintering of the second area and the first area share the same controller; and the variable resistor is omitted from the pressure-applying component of this comparative example.

[0063] In the laser-assisted sintering method of the present comparative example, steps S2 and S3 both omit the process in which the variable resistor adjusts its own resistance value according to the distance between the scanning point and the probe; and the first laser power and the second laser power are the same, both are 25W; the first reverse bias voltage and the second reverse bias voltage are also the same, both are 17V.

[0064] Performance Testing

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

[0066] Table 1

[0067]

[0068]

[0069] It can be seen from Table 1 that the contact resistivity of the left half of the battery cell processed by the existing laser-assisted sintering method of Comparative Example 1 is large, while the contact resistivity of the right half is small, that is, the contact resistivity of different positions of the battery cell processed by Comparative Example 1 is obviously unevenly distributed.

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

[0071] Table 2

[0072]

[0073]

[0074] From Table 2, it can be seen that the contact resistivity difference between the left and right halves of the cell treated by the method for improving the contact uniformity of laser-assisted sintering in Example 1 is not obvious. Therefore, compared with Comparative Example 1, the contact resistivity uniformity of different positions of the cell treated in Example 1 is significantly improved.

[0075] 3. The performance tests were performed on the cells after treatment in Comparative Example 1 and Example 1, and the test data are shown in Table 3. 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] It can be seen from Table 3 that compared with Comparative Example 1, the photoelectric conversion efficiency, open circuit voltage, short circuit current and fill factor of the solar cell treated by the method for improving laser-assisted sintering contact uniformity according to Example 1 are all improved.

[0079] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0080] The technical solution provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for improving contact uniformity of laser-assisted sintering, characterized in that: The process steps include: S1, prepare a cell and a processing device for improving laser-assisted sintering; the cell comprises a silicon substrate, and grid lines are arranged on both the front and back sides of the silicon substrate, and the grid lines include cross-connected main grids and fine grids; The processing device includes a laser, a pressure component and a controller; the pressure component includes a probe, a variable resistor, a power supply and a conductive platform for carrying a battery cell, the positive electrode of the power supply is electrically connected to the back of the battery cell through the conductive platform, and the negative electrode of the power supply is electrically connected to the front main grid through the variable resistor and the probe in sequence; S2, the probe presses the main grid of the first area on the front side of the battery cell, the controller controls the laser to use the first laser power to laser scan the second area on the front side of the battery cell along the fine grid direction, and controls the pressure component to apply a first reverse bias to the battery cell, and the variable resistor adjusts its own resistance value according to the distance between the scanning point and the probe to balance the bias difference at different scanning points, so that the second area is laser-assisted sintered; S3. The probe presses the main grid of the second area on the front side of the battery cell. The controller controls the laser to use the second laser power to laser scan the first area on the front side of the battery cell along the fine grid direction, and controls the pressure-applying component to apply a second reverse bias 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 difference at different scanning points, so that the first area can be laser-assisted sintered.

2. A method for improving contact uniformity of laser-assisted sintering according to claim 1, characterized in that: The first laser power is smaller than the second laser power, and the first reverse bias voltage is smaller than the second reverse bias voltage.

3. A method for improving contact uniformity of laser-assisted sintering according to claim 1 or 2, characterized in that: 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-applying component is 1-25V.

4. The method for improving contact uniformity of laser-assisted sintering according to claim 3, 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.

5. A method for improving contact uniformity of laser-assisted sintering according to claim 1 or 2, characterized in that: In steps S2 and S3, the resistance value adjustment range of the variable resistor is controlled within 0-10Ω; When the scanning point is close to the probe, the resistance value of the variable resistor increases; when the scanning point is far away from the probe, the resistance value of the variable resistor decreases to balance the bias voltage difference at different scanning points.

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

7. The method for improving contact uniformity of laser-assisted sintering according to claim 1, characterized in that: The first area and the second area do not completely overlap, and the first area and the second area overlap to cover the grid line area of ​​the battery cell.

8. The method for improving contact uniformity of laser-assisted sintering according to claim 7, characterized in that: The first area and the second area are respectively the left half area and the right half area of ​​the battery cell.

9. A processing device for improving laser-assisted sintering, characterized in that: A method for improving contact uniformity in laser-assisted sintering as claimed in any one of claims 1 to 8; The processing device includes a laser for laser scanning the front side of the battery cell, a pressure component and a controller connecting the laser and the pressure component; the pressure component includes a probe for pressing the main grid on the front side of the battery cell, a variable resistor, a power supply and a conductive platform for supporting the battery cell, the variable resistor is electrically connected to the probe, the conductive platform is electrically connected to the back side of the battery cell, and the negative and positive electrodes of the power supply are electrically connected to the variable resistor and the conductive platform respectively.

10. A processing device for improving laser assisted sintering according to claim 9, characterized in that: The conductive platform is a copper plate; the cell is a crystalline silicon solar cell; There are two controllers, and the two controllers respectively control the application of the first reverse bias voltage and the second reverse bias voltage.

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