Method and apparatus for removing a solar cell anti-reflective layer

Abstract

The present application belongs to the technical field of solar cell production, and particularly relates to a method and device for removing the anti-reflection layer of a solar cell. The method comprises the following steps: S1, positioning the contact area of the electrode and the test fixture; S2, using ultraviolet picosecond laser to scan and etch the anti-reflection layer in the contact area to expose the substrate covered by the anti-reflection layer; S3, using inert gas to clean the etching area during etching; S4, after etching is completed, performing quality detection on the cell to verify the etching effect, and the quality detection comprises at least one of anti-reflection layer residual amount detection, substrate integrity detection, surface topography detection, and contact performance detection. The method realizes precise removal of the anti-reflection layer, can improve the problem of high damage degree of the substrate, thereby can significantly reduce the test error in subsequent IV test, and thus improves the authenticity and reliability of the test result.

Description

Technical Field

[0001] This invention belongs to the field of solar cell manufacturing technology, and specifically relates to a method and apparatus for removing the antireflection layer of a solar cell. Background Technology

[0002] Solar cells have become a research hotspot in the field of solar energy due to their high conversion efficiency and low temperature coefficient. Especially for heterojunction cells, their structure typically includes an N-type monocrystalline silicon substrate, an intrinsic amorphous silicon passivation layer deposited sequentially on the front and back sides of the substrate, a doped amorphous silicon layer, a transparent conductive oxide layer, and a metal electrode. To minimize reflection losses on the light-receiving surface, an anti-reflection layer is usually deposited across the entire surface of the cell.

[0003] After battery manufacturing is completed, IV testing (current-voltage testing) is required to evaluate its electrical performance. Since the antireflective layer is deposited across the entire surface, its insulation properties can increase test errors. Therefore, it is necessary to remove the antireflective layer from the area where the test fixture contacts the battery to improve accuracy. However, existing techniques typically employ mechanical scraping or mask chemical etching, which causes significant damage to the substrate, leading to substantial errors in IV testing. Summary of the Invention

[0004] To address the issue of high susceptibility to damage during the removal of antireflective layers, this invention provides a method and apparatus for removing antireflective layers from solar cells.

[0005] According to an embodiment of the present invention, a first aspect provides a method for removing an antireflective layer from a solar cell, the solar cell comprising electrodes and an antireflective layer covering the electrodes, the method comprising: Step S1: Locate the contact area between the electrode and the test fixture; Step S2: Use an ultraviolet picosecond laser to scan and etch the antireflection layer in the contact area to expose the substrate covered by the antireflection layer; Step S3: During the etching process, inert gas is used to purge and clean the etched area; Step S4: After etching is completed, the battery is subjected to quality inspection to verify the etching effect. The quality inspection includes at least one of the following: antireflection layer residue detection, substrate integrity detection, surface morphology detection, and contact performance detection.

[0006] In some embodiments, step S1 further includes: Step S11, acquire image data: Place the battery on the displacement platform and acquire a panoramic image of the battery as image data using an industrial camera; Step S12, Extract contour features: Use the algorithm model to extract the contour features of the electrodes from the image data; Step S13, analyze the deviation value: compare the spatial coordinates of the contour feature with the contact reference of the test fixture, and analyze the deviation value between the actual position of the current battery and the standard position. The deviation value includes the first deviation value in the electrode length direction and the second deviation value in the electrode width direction. Step S14, Position Compensation: Move the displacement platform in the opposite direction of the deviation value, with the amount of movement equal to the absolute value of the deviation value, so that the outline of the electrode is aligned with the contact reference, thereby locating the contact area; Step S15, manual verification: Project the crosshair laser onto the battery surface and visually observe whether the center of the crosshair laser coincides with the center of the contact area; if the deviation exceeds the deviation verification threshold, then calibration is performed.

[0007] In some embodiments, step S2 further includes: Step S21, set laser parameters: set the wavelength range to 266nm~355nm for ultraviolet picosecond laser, and select either constant energy scanning strategy or multi-level energy decreasing scanning strategy. Step S22, Spot shaping: First, a diffractive optical element is used to convert the Gaussian spot of the ultraviolet picosecond laser into a flat-top spot, and then a lens is used to focus the flat-top spot onto the contact area so that the focal plane error does not exceed ±10μm; Step S23, set the scanning path: control the ultraviolet picosecond laser to scan and etch the contact area along a preset path, wherein the preset path is a path that scans the entire contact area in a serpentine manner, or a path that first scans the edge of the pre-contact area in a circular manner, and then scans the interior of the pre-contact area in a serpentine manner. Step S24, Real-time monitoring: Use a monitoring camera to collect images of the etched area in real time, and use real-time grayscale value analysis to determine the etch progress. When the real-time grayscale value is stable at the grayscale threshold, stop the etch.

[0008] In some embodiments, in step S23, the contact area includes a middle area and two end areas, the two end areas being located at both ends of the electrode length direction and being arc-shaped; The middle region is scanned at a first scanning speed, and the two end regions are laser scanned at a second scanning speed, wherein the first scanning speed is greater than the second scanning speed.

[0009] In some embodiments, the antireflective layer is magnesium fluoride, and the substrate covered by the antireflective layer is tin. In step S22, the power ratio of the flat-top region of the flat-top spot is not less than 90%, the spot size is 50μm to 100μm, the spot overlap area is 30% to 50%, and the focal plane error does not exceed ±10μm. The grayscale threshold in step S24 is 130±5.

[0010] In some embodiments, the wavelength of the ultraviolet picosecond laser in step S21 is 355nm, and it adopts a multi-level energy decreasing scanning strategy. The energy density of the first pulse is 80mJ / cm², and it is gradually reduced to 50mJ / cm² thereafter. The number of etching cycles is 5 to 8. The preset path in step S23 is a serpentine scanning path of the entire contact area. During the entire serpentine scanning process, the first scanning speed of the straight scanning segment is 2300mm / s to 2500mm / s, and the second scanning speed of the arc transition segment is 1100mm / s to 1300mm / s. or The ultraviolet picosecond laser in step S21 has a wavelength of 266 nm and adopts a constant energy scanning strategy. The single pulse energy density is 60 mJ / cm², and the etching number is 1 to 3 times. The preset path in step S23 is to first scan the edge of the pre-contact area in a circular motion, and then scan the inside of the pre-contact area in a serpentine motion. During the circular scanning process, the scanning speed is 500 mm / s. During the serpentine scanning process, the first scanning speed of the straight scanning segment is 2300 mm / s to 2500 mm / s, and the second scanning speed of the arc transition segment is 1100 mm / s to 1300 mm / s.

[0011] In some embodiments, step S3 further includes: Step S31, set the purging parameters: use a nozzle to blow inert gas toward the etching area, the purging direction of the inert gas is at an angle of 10° to 65° with the laser scanning direction, and the purging pressure is 0.03MPa to 0.15MPa; Step 32, Residue Collection: A negative pressure collector is installed below the etched area to adsorb impurities generated during etching.

[0012] In some embodiments, step S4 includes at least one of the following sub-steps: Step S41, Antireflection layer residue detection: The distribution of the antireflection layer residue is determined by scanning the spectral ellipsometry, and the cross-sectional morphology and elemental analysis of key points are verified by scanning electron microscopy combined with energy dispersive spectroscopy. Finally, the continuous residue in the etched area and the total residue at the sampling points are used as dual judgment criteria. Step S42, Substrate integrity detection: A four-probe tester is used to obtain the sheet resistance values ​​of the etched area and the unetched area respectively. By analyzing the average value of the two values, the integrity of the substrate during the etching process is determined. Step S43, Surface morphology inspection: Use an atomic force microscope to inspect the scratches or depressions, as well as the surface roughness of the etched and unetched areas, in order to determine the impact of the etching process on the substrate surface. Step S44, Contact performance testing: By performing IV tests on the battery before and after etching, the changes in its series resistance and fill factor are obtained to determine the impact of the etching process on the contact performance.

[0013] In some embodiments, a pretreatment step S0 is further included: cleaning and drying the battery to remove oil and dust from the battery surface; wherein step S0 further includes: Step S01, Cleaning the battery: A mixture of isopropanol and deionized water at a volume ratio of 1:3 is used as the cleaning solution. The equipment used includes an ultrasonic cleaner, and the cleaning time is 5 min to 8 min. Step S02, drying the battery: First, use an air knife to blow inert gas onto the battery surface at a wind speed of 10m / s to 15m / s and a temperature of 22℃ to 26℃; then use a vacuum drying oven to dry the moisture content on the battery surface to no more than 0.1mg / cm², with a vacuum degree of less than 1Pa, a drying temperature of 35℃ to 45℃, and a drying time of 30min to 40min.

[0014] According to an embodiment of the present invention, a second aspect provides an apparatus for removing an antireflective layer of a solar cell, comprising: A positioning module is used to locate the contact area between the electrodes of the battery and the test fixture; A laser etching module is used to scan and etch the antireflection layer in the contact area using an ultraviolet picosecond laser to expose the substrate covered by the antireflection layer. The purging and cleaning module is used to purge and clean the etched area with inert gas during the etching process; and The quality inspection module is used to perform quality inspection on the battery after etching to verify the etching effect. The quality inspection includes the inspection of at least one of the following: residual amount of antireflection layer, substrate integrity, surface morphology and contact performance. The positioning module includes: A displacement platform for supporting and moving the battery; An industrial camera is used to acquire image data of the battery; an image processing unit is used to acquire image data of the battery and extract the contour features of the electrodes from the image data using an algorithm model. An image processing unit is used to extract the contour features of the electrodes from the image data using an algorithm model; The deviation analysis unit is used to compare the contour features with the contact reference of the test fixture in spatial coordinates and analyze the deviation value between the actual position of the current battery and the standard position. A controller is configured to control the movement of the displacement platform based on the deviation value, so that the contour edge of the electrode is aligned with the contact reference; and A laser line projector is used to emit a crosshair laser and project it onto the surface of the battery for manual verification of positioning accuracy. The laser etching module includes: Ultraviolet picosecond laser, used to generate ultraviolet picosecond laser; The optical path shaping unit includes a diffractive optical element for converting a Gaussian spot into a flat-top spot, and a lens for focusing the flat-top spot onto the contact area. A scanning galvanometer is used to control the ultraviolet picosecond laser to scan and etch the contact area along a preset path; and A monitoring camera is used to acquire images of the etched area in real time and to determine the etching progress through real-time grayscale value analysis. The purging and cleaning module includes: Nozzles are used to blow inert gas toward the etched area; and Negative pressure collector is used to adsorb impurities generated during etching; The quality inspection module includes an instrument for at least one of the following tests: Spectroscopic ellipsometry, scanning electron microscope and energy dispersive spectroscopy are used to detect the amount of antireflection layer residue; A four-probe tester is used to perform substrate integrity testing. Atomic force microscopy is used to perform surface morphology inspection; and The IV tester is used to perform contact performance testing.

[0015] The method for removing the antireflective layer of solar cells according to the present invention achieves precise removal of the antireflective layer through the cooperation of steps S1 to S4, namely, accurately locating the contact area, etching with ultraviolet picosecond laser, cleaning during the etching process, and quality inspection after etching. This improves the problem of high damage to the substrate, thereby significantly reducing the test error in subsequent IV tests and improving the authenticity and reliability of the test results. Attached Figure Description

[0016] Figure 1 This is a comparative structural diagram of a solar cell before and after etching, representing one embodiment of this application. Figure 2 This is a flowchart of a method for removing the antireflective layer of a solar cell according to one embodiment of this application; Figure 3This is a schematic diagram of the contact area in one embodiment of this application; Figure 4 This is a comparative test result diagram of Embodiment 4 of this application.

[0017] In the figure: Electrode 100; Conductive layer 200; Anti-reflective layer 300; Etched area 400; Middle area 410; End area 420. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] The orientations or positional relationships indicated in this specification are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the purpose of simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0020] In existing technologies, antireflective layers are typically deposited on the entire surface of the battery, covering the electrode surface and thus providing insulation. When performing IV testing, the test fixture contacts the electrodes covered with the antireflective layer. Due to the insulation properties of the antireflective layer, a large contact resistance is generated, resulting in an overestimation of the series resistance (Rs) and an underestimation of the fill factor (FF), leading to significant test errors and failing to accurately reflect battery performance.

[0021] like Figure 1 As shown, to solve this problem, the antireflective layer 300 at the contact location of electrode 100 needs to be removed. Existing technologies typically employ mechanical scraping or mask chemical etching to remove the antireflective layer 300. However, mechanical scraping easily damages the underlying substrate and leaves uneven residue; mask chemical etching is a complex process, and the chemicals can easily penetrate the substrate edges, causing corrosion and resulting in significant damage to the substrate, thus leading to larger errors in IV testing.

[0022] See details Figure 2 This embodiment provides a method for removing an antireflective layer on a solar cell. The solar cell includes an electrode 100 and an antireflective layer 300 covering the electrode 100. The method includes: Step S1: Position the contact area 400 between the electrode 100 and the test fixture; Step S2: In the contact area 400, the antireflection layer 300 is scanned and etched using an ultraviolet picosecond laser to expose the substrate covered by the antireflection layer 300. Step S3: During the etching process, inert gas is used to purge and clean the etched area; Step S4: After etching is completed, the battery is subjected to quality inspection to verify the etching effect. The quality inspection includes at least one of the following: antireflection layer residue detection, substrate integrity detection, surface morphology detection, and contact performance detection.

[0023] It should be noted that in some batteries, the antireflection layer 300 is directly covered on the electrode 100, and the electrode 100 serves as a substrate covered with the antireflection layer 300; in some batteries, a conductive layer 200 is also included between the electrode 100 and the antireflection layer 300, and the conductive layer 200 serves as a substrate.

[0024] The processing method of this embodiment, through the cooperation of steps S1 to S4, namely, accurately locating the contact area 400, using ultraviolet picosecond laser for etching, purging and cleaning during the etching process, and quality inspection after etching, achieves precise removal of the antireflection layer 300, which can improve the problem of high damage to the substrate. This can significantly reduce the test error in the subsequent IV test, thereby improving the authenticity and reliability of the test results.

[0025] Step S1 further includes the following sub-steps: Step S11, acquire image data: Place the battery on the displacement platform and acquire a panoramic image of the battery as image data using an industrial camera.

[0026] Step S12, extract contour features: use the algorithm model to extract the contour features of electrode 100 from the image data.

[0027] In one embodiment, the contour features of electrode 100 are extracted from image data by a U-Net deep learning model pre-trained in the image processing unit. The U-Net model is suitable for accurately segmenting the contour of electrode 100 with well-defined geometric boundaries from complex backgrounds.

[0028] Step S13, analyze the deviation value: The deviation analysis unit compares the spatial coordinates of the contour feature with the contact reference of the test fixture to analyze the deviation value between the actual position of the current battery and the standard position. The deviation value includes the first deviation value in the length direction of the electrode 100 and the second deviation value in the width direction of the electrode 100.

[0029] In one embodiment, the contact reference of the test fixture is a fixed coordinate preset in the deviation analysis unit. When the battery moves to the standard position, the outline of the battery electrode 100 aligns with the contact reference of the test fixture, ensuring that the picosecond laser can accurately scan the etched contact area 400. The contact reference of the test fixture specifically refers to the component of the fixture that needs to contact the electrode 100, which can be existing components such as pressure strips or probes.

[0030] The outline features of electrode 100 and the contact reference pattern of the fixture are preferably in CAD format. CAD format graphic data facilitates high-precision numerical calculations and deviation analysis. For example, if the first deviation value is found to be +2μm and the second deviation value is -1μm during the comparison process, calibration is required in subsequent steps.

[0031] Step S14, Position Compensation Control: By controlling the displacement platform to move in the opposite direction of the deviation value, the amount of movement is equal to the absolute value of the deviation value, so that the contour edge of the electrode 100 is aligned with the contact reference, thereby accurately positioning the contact area 400.

[0032] In one embodiment, the controller controls the moving platform to move the battery based on the deviation value to achieve automatic compensation. For example, when the first deviation value is +2μm and the second deviation value is -1μm, the moving platform moves the battery -2μm along the length direction of the electrode 100 and +1μm along the width direction of the electrode 100 to achieve alignment.

[0033] Step S15, manual verification: Project the crosshair laser onto the battery surface and visually observe the overlap between the center of the crosshair laser and the center of the contact area 400; if the deviation exceeds the verification threshold, then calibration is performed.

[0034] In one embodiment, the wavelength of the cross laser emitted by the laser line projector is preferably 650 nm, and the line width is no more than 50 μm. The verification threshold is set according to the processing accuracy requirements. In this embodiment, the verification threshold is preferably ±2 μm. If the deviation between the cross laser and the center of the contact area exceeds this verification threshold, calibration is required to ensure accurate positioning of the contact area 400.

[0035] Step S2 further includes sub-steps S21-S24: Step S21: Set laser parameters. Use an ultraviolet picosecond laser with a wavelength range of 266nm to 355nm to scan and etch the contact area 400. Select either a constant energy scanning strategy or a multi-level energy decreasing scanning strategy. The constant energy scanning strategy ensures uniform etching along the scanning path through a constant energy output. The multi-level energy decreasing scanning strategy effectively avoids damage to the substrate beneath the antireflective layer 300 due to excessive energy, while ensuring effective removal of the antireflective layer 300.

[0036] In one embodiment, the ultraviolet picosecond laser emits ultraviolet picosecond laser light with a wavelength range of 355nm. This wavelength of ultraviolet picosecond laser light combines high single-photon energy with extremely high industrial-grade average power, enabling high-throughput processing that balances precision and efficiency. It is currently a relatively mature ultraviolet picosecond laser solution in the industrial field. The multi-stage energy-decreasing scanning strategy specifically refers to the fact that the energy density of the first single pulse and the energy density of subsequent single pulses gradually decrease. This strategy can protect the substrate material and improve surface finish while ensuring penetration efficiency.

[0037] In one embodiment, the ultraviolet picosecond laser has a wavelength range of 266 nm. This wavelength of ultraviolet picosecond laser has a higher single-pulse etching rate, which helps to obtain a cleaner, less damaged processed surface and reduce the total number of etching passes. It should be noted that in actual processing, the wavelength range of the ultraviolet picosecond laser can be selected according to the actual accuracy requirements and cost budget.

[0038] Step S22, spot shaping: First, a diffractive optical element is used to convert the Gaussian spot of the ultraviolet picosecond laser into a flat-top spot, and then a lens is used to focus the flat-top spot onto the contact area 400.

[0039] Because unshaped ultraviolet picosecond lasers typically exhibit a Gaussian distribution (high energy at the center and low energy at the edges), this can lead to over-ablation in the center and under-ablation at the edges of the processing area. In one embodiment, a diffractive optical element is used to convert the Gaussian spot into a flat-top spot, preferably with a spot size of 50μm to 100μm. The power proportion of the flat-top region of this spot is relatively large, for example, not less than 90%, which enables almost the entire spot to uniformly remove the antireflection layer 300, ensuring consistent etching depth. A lens is then used to focus the flat-top spot onto the contact area 400, ensuring that the focal plane error does not exceed ±10μm to maintain the consistency of the spot size and guarantee uniform etching effect. Using this optimized flat-top spot for etching creates a gentle slope of no more than 1° at the edges of the etched area, which helps avoid stress concentration problems caused by steep edges, thereby improving the structural reliability of the etched area.

[0040] Step S23: Set the scanning path and control the ultraviolet picosecond laser to scan and etch the contact area 400 along the preset path. The preset path is either a serpentine scanning path of the entire contact area 400, or a path that first scans the edge of the pre-contact area in a circular motion and then scans the interior of the pre-contact area in a serpentine motion.

[0041] In the serpentine scanning path across the entire contact area 400, the scanning galvanometer minimizes time through continuous reciprocating scanning, ensuring overall etching efficiency and uniformity of the heat-affected zone. In the path that first uses a circular scan of the pre-contact area edge and then a serpentine scan of the pre-contact area interior, the circular scan pre-closes the edge to suppress lateral heat diffusion and stress release, preventing edge chipping or cracking due to insufficient edge constraint during the internal serpentine scan.

[0042] In some embodiments, see details. Figure 3 The contact area 400 includes a middle area 410 and two end areas 420, which are located at both ends of the electrode 100 along its length and are arc-shaped. By providing arc-shaped transition portions at both ends of the contact area 400, energy concentration caused by laser right-angle scanning at the edge of the contact area 400 is avoided. Furthermore, the middle region 410 is scanned at a first scanning speed, while the two end regions 420 are scanned at a second scanning speed, with the first scanning speed being greater than the second scanning speed. The higher scanning speed in the middle region 410 ensures the smoothness of the etched surface. The reduced scanning speed in the end regions 420 matches the acceleration and deceleration processes caused by changes in path curvature, preventing energy loss or insufficient etching depth at the foldback points. Furthermore, during the serpentine scanning process, the scanning direction is along the length of the electrode 100, and a reciprocating straight scanning segment is formed in the width direction of the electrode 100. The light spots overlap between adjacent straight scanning segments, and the gap between adjacent scanning bands is improved by an appropriate amount of overlap.

[0043] Step S24: Real-time monitoring. Use a monitoring camera to collect images of the etched area in real time. Analyze the etch progress using real-time grayscale values. Stop etching when the real-time grayscale values ​​are stable within the grayscale threshold range.

[0044] In one embodiment, the monitoring camera preferably employs a charge-coupled device (CCD) image sensor with a resolution selectable at 1280 pixels × 720 pixels. The grayscale threshold is determined based on the grayscale values ​​of the antireflective layer 300 and the substrate. For example, the antireflective layer 300 is magnesium fluoride (MgF2) with a grayscale value of 180–200; the substrate is tin (Sn) with a grayscale value of 120–140. Therefore, the grayscale threshold is set to 130 ± 5, using the substrate's grayscale value as a reference. It should be noted that since the grayscale threshold needs to be determined based on the substrate material, this embodiment will not elaborate further.

[0045] Step S3 further includes sub-steps S31-S32: Step S31: Set the purging parameters. Use a nozzle to blow inert gas toward the etching area. The purging direction of the inert gas is at an angle of 10° to 65° with the scanning direction. The purging pressure is 0.03MPa to 0.15MPa.

[0046] In one embodiment, the inert gas can be conventional argon or nitrogen, with a purity of not less than 99%. Purge during etching prevents impurities from settling in the processed area or in front of the laser spot, ensuring processing quality. The nozzle can be a customized fan-shaped nozzle, for example, with an outlet width of 5mm, an orifice diameter of 0.5mm, and an outlet distance of 8mm from the battery surface. It should be noted that the structure of the customized fan-shaped nozzle needs to be adjusted according to factors such as the battery size and picosecond laser parameters; therefore, this embodiment will not elaborate on it.

[0047] Step S32, Residue Collection: A negative pressure collector is set up below the etched area to adsorb impurities generated during etching.

[0048] In one embodiment, the vacuum degree of the negative pressure collector can be set to -0.08MPa, the size of the collection port is 20mm×10mm, and a filter membrane with a pore size of 0.1μm can be set in the collection port as needed to make its impurity collection rate higher than 99.5%, which can effectively prevent impurities from being deposited again and contaminating the battery.

[0049] Step S4 further includes at least one sub-step S41-S44: Step S41, Antireflection layer residue detection: The distribution of antireflection layer residue is determined by scanning with a spectral ellipsometry, and the cross-sectional morphology and elemental analysis of key points are verified by scanning electron microscopy combined with energy dispersive spectroscopy. Finally, the continuous residue in the etched area and the total residue at the sampling points are used as the dual criteria for determining whether the process is qualified.

[0050] In one embodiment, a spectral ellipsometry is used to obtain the thickness distribution map of the antireflective layer over the entire area. Specific points are then randomly selected for inspection (such as thickness anomalies, both ends, and the middle). The cross-section is observed using a scanning electron microscope, and the elemental content is analyzed using an energy dispersive spectroscopy (EDS) instrument for final confirmation. If the continuous residual amount in the etched area and the total residual amount at the sampled points all meet the requirements, then the residual amount of the antireflective layer is confirmed to meet the requirements.

[0051] Step S42, Substrate integrity detection: A four-probe tester is used to obtain the sheet resistance values ​​of the etched area and the unetched area respectively. By analyzing the average value of the two values, the integrity of the substrate during the etching process is determined.

[0052] In one embodiment, a four-probe tester is used to obtain the sheet resistance values ​​of the etched area and the unetched area. When the unetched area has high impedance due to the insulating anti-reflection layer 300 covering it, and the sheet resistance of the etched area is close to the standard resistance value, it is confirmed that the substrate is intact and undamaged.

[0053] Step S43, Surface morphology inspection: Atomic force microscopy is used to inspect scratches or depressions, and to inspect the surface roughness of the etched area and the unetched area to determine the impact of the etching process on the substrate surface.

[0054] In one embodiment, the surface morphology inspection requires that the surface after etching has no obvious scratches or depressions, and the roughness is within an acceptable range. For example, the roughness Ra of the unetched area is in the range of 0.7 nm to 0.9 nm, and the roughness of the etched area is in the range of 1.1 nm to 1.3 nm, then the surface morphology is confirmed to meet the requirements.

[0055] Step S44, Contact performance testing: By performing IV tests on the battery before and after etching, the changes in its series resistance and fill factor are obtained to determine the impact of the etching process on the contact performance.

[0056] In one embodiment, by analyzing the reduction in series resistance and the improvement in fill factor before and after etching, when the series resistance decreases and the fill factor increases, and both are close to the standard value, it indicates that the contact performance after etching is closer to the actual level of the battery, thus verifying the effectiveness of the etching process.

[0057] The method in this embodiment further includes a pretreatment step S0, in which the battery is cleaned and dried to remove oil and dust from its surface. Step S0 further includes sub-steps S01-S02: Step S01, Cleaning the battery: A mixture of isopropanol and deionized water at a volume ratio of 1:3 is used as the cleaning solution. The equipment used includes an ultrasonic cleaner, preferably with a power of 300W and a frequency of 40kHz. The cleaning time is 5 to 8 minutes to clean the oil and dust on the surface of the battery.

[0058] Step S02, drying the battery: First, use an air knife to blow inert gas onto the battery surface at a wind speed of 10m / s to 15m / s and a temperature of 22℃ to 26℃. Then, use a vacuum drying oven to dry the surface moisture content of the battery to no more than 0.1mg / cm². The vacuum degree of the drying oven is less than 1Pa, the drying temperature is 35℃ to 45℃, and the drying time is 30 to 40 minutes. It should be noted that the battery cleaning and drying processes can be adapted to other existing processes as needed, ensuring that the cleanliness and moisture content of the battery surface meet the requirements.

[0059] Example 2 Taking one of the heterojunction solar cells as an example, the substrate of the heterojunction solar cell is an N-type monocrystalline silicon wafer. The electrode 100 on the front side of the N-type monocrystalline silicon wafer is covered with a conductive layer 200 and an anti-reflection layer 300 in sequence. The conductive layer 200 is made of tin (Sn), and the anti-reflection layer 300 is made of magnesium fluoride (MgF2).

[0060] In step S21, the wavelength of the ultraviolet picosecond laser is 355nm, its single pulse energy is 5.12μJ, its pulse width is 15ns, and its repetition frequency is 50kHz. It adopts a multi-level energy reduction scanning strategy, with the initial pulse energy density being 80mJ / cm², and subsequently decreasing to 50mJ / cm², and the number of etching cycles being 5 to 8.

[0061] In step S22, the overlap rate of adjacent light spots is 40%.

[0062] In step S23, the preset path is a serpentine scanning path of the entire contact area 400. During the serpentine scanning process, the middle area 410 is scanned at a first scanning speed of 2300mm / s to 2500mm / s, and the end area 420 is scanned at a second scanning speed of 1100mm / s to 1300mm / s.

[0063] In step S31, the inert gas ejected from the nozzle is nitrogen gas with a purity greater than 99%, the purging direction of the inert gas is at an angle of 15° to 30° with the laser scanning direction, and the purging pressure is 0.03MPa to 0.04MPa.

[0064] In step S41, the residual amount of magnesium fluoride is detected by scanning electron microscopy and energy dispersive spectroscopy. If the continuous residual amount is less than or equal to 2 nm and the total residual amount of the sampling points is less than 2 nm, then the residual amount of the antireflection layer is confirmed to meet the requirements.

[0065] In step S42, a four-probe tester is used to obtain sheet resistance values ​​at 20 test points in the etched area and at 5 test points in the unetched area. When the average sheet resistance of the etched area is 45.0 ± 0.5 Ω / □ and the average sheet resistance of the unetched area is greater than 500 Ω / □, the substrate is confirmed to be intact.

[0066] In step S43, an atomic force microscope is used to detect that there are no scratches or dents, and the surface roughness Ra of the etched area is 1.1 nm to 1.3 nm, and the surface roughness Ra of the unetched area is 0.7 nm to 0.9 nm. If the surface morphology meets the requirements, it is confirmed that the surface morphology meets the requirements.

[0067] In step S44, the series resistance Rs before etching is 8.5Ω and the fill factor is 78.2%; the series resistance after etching is 3.2Ω and the fill factor is 80.1%, which is closer to the actual level of the battery.

[0068] Example 3 The main differences between this embodiment and Embodiment 2 are steps S21, S23, and 31.

[0069] In step S21, the wavelength of the ultraviolet picosecond laser is 266nm, its single pulse energy density is 60mJ / cm², its single pulse energy is 3.84μJ, its pulse width is 10ns, and its repetition frequency is 30kHz; a constant energy scanning strategy is used, and the number of etching cycles is 1 to 3.

[0070] In step S23, the preset path is to first scan the edge of the pre-contact area in a circular motion, and then scan the path inside the pre-contact area in a serpentine motion. During the circular scanning process, the scanning speed is 500 mm / s to outline the contour. During the serpentine scanning process, the middle area 410 is scanned at a first scanning speed of 2300 mm / s to 2500 mm / s, and the end area 420 is scanned at a second scanning speed of 1100 mm / s to 1300 mm / s.

[0071] In step S31, the inert gas ejected from the nozzle is argon gas with a purity greater than 99%, the purging direction of the inert gas is at an angle of 15° to 30° with the laser scanning direction, and the purging pressure is 0.13MPa to 0.15MPa.

[0072] In this embodiment, a 266nm wavelength ultraviolet picosecond laser is used. A preset path is selected for scanning etching, which first scans the edge of the pre-contact area in a ring and then scans the inside of the pre-contact area in a serpentine pattern. This can accurately remove the anti-reflection layer 300 and improve the problem of substrate damage.

[0073] Example 4 This embodiment aims to verify the advantages of the antireflection layer 300 removal method provided by the present invention compared with the prior art. The specific operation is as follows: 100 heterojunction solar cells produced in the same batch were selected as test samples and randomly divided into three groups of test sheets, 30 sheets in each group, with the remaining 10 sheets reserved for later use. The first group of test sheets had the antireflection layer 300 (MgF2) removed using the method provided by the present invention; the second group of test sheets had the antireflection layer 300 removed using a mechanical scraping method; and the third group of test sheets had the antireflection layer 300 removed using a mask chemical etching method.

[0074] After removing the antireflective layer 300, key parameters were tested on each group of experimental wafers. The tests included: the average residual amount of the antireflective layer 300, the average substrate damage rate (based on the number and percentage of damaged cells), and the product pass rate (pass criteria being a fill factor within the true range and no substrate damage). The test results are attached. Figure 4 .

[0075] Test data shows that in the first group (this method group): the average residual amount of antireflective layer 300 is 3nm, the substrate damage rate is 0 (0 / 30), and the product qualification rate is 98% (29 / 30).

[0076] Group 2 (Mechanical Scraping Group): The average residual amount of antireflective layer 300 was 25nm, the substrate damage rate was 30% (9 / 30), and the product qualification rate was 63% (19 / 30).

[0077] Group 2 (Mask Chemical Etching Group): The average residual amount of the antireflective layer 300 was 15nm, the substrate damage rate was 23% (7 / 30), and the product qualification rate was 83% (25 / 30).

[0078] Experimental results show that, compared with mechanical scraping and mask baffle combined with chemical etching, the laser removal method provided by this invention can effectively reduce the average residual amount of antireflection layer 300 and improve substrate damage, and significantly improve product yield and ensure process stability.

[0079] Example 5 This embodiment provides a device for removing the antireflection layer of a solar cell, used to perform the method described above to remove the antireflection layer 300 covering the solar cell electrode 100, exposing the underlying substrate (such as the conductive layer 200 or the electrode 100 itself). The device includes a positioning module, a laser etching module, a purging and cleaning module, and a quality inspection module.

[0080] The positioning module in this embodiment is used to position the contact area 400 between the battery electrode 100 and the test fixture. Specifically, the positioning module includes a displacement platform, an industrial camera, an image processing unit, a deviation analysis unit, a controller, and a laser line projector.

[0081] The system includes a displacement platform for supporting and moving the battery; an industrial camera for acquiring image data of the battery; an image processing unit for acquiring image data of the battery and extracting the contour features of the electrode 100 from the image data using an algorithm model; an image processing unit electrically connected to the industrial camera for extracting the contour features of the electrode 100 from the image data using an algorithm model; a deviation analysis unit for comparing the contour features with the contact reference of the test fixture in spatial coordinates to analyze the deviation value between the actual position of the battery and the standard position; a controller electrically connected to the deviation analysis unit and the displacement platform for controlling the movement of the displacement platform according to the deviation value to align the contour edge of the electrode 100 with the contact reference; and a laser line projector for emitting a crosshair laser and projecting it onto the battery surface for manual verification of positioning accuracy.

[0082] It should be noted that the image processing unit, deviation analysis unit, and controller in this embodiment are all integrated into an existing industrial control computer, which can run deep learning algorithms and process detection data, and send precise control commands to each actuator.

[0083] The laser etching module of this embodiment is used to scan and etch the antireflection layer 300 in the contact area 400 using an ultraviolet picosecond laser, so as to expose the substrate covered by the antireflection layer 300. Specifically, the laser etching module includes an ultraviolet picosecond laser, an optical path shaping unit, a scanning galvanometer, and a monitoring camera.

[0084] The ultraviolet picosecond laser is used to generate ultraviolet picosecond laser light. The optical path shaping unit is set in the output optical path of the ultraviolet picosecond laser and includes diffractive optical elements and lenses. The diffractive optical elements are used to convert the Gaussian spot output by the laser into a flat-top spot, and the lenses are used to precisely focus the flat-top spot onto the contact area 400 on the surface of the battery. The scanning galvanometer is used to receive the shaped laser beam and control the laser to perform high-speed scanning etching of the contact area 400 along a preset path. The monitoring camera is coaxially mounted above the scanning galvanometer to acquire images of the etched area in real time and to determine the etching progress through grayscale value analysis.

[0085] The purging and cleaning module of this embodiment is used to purge and clean the etched area with inert gas during the etching process. Specifically, the purging and cleaning module includes a nozzle and a negative pressure collector. The nozzle is used to blow inert gas toward the etched area; the negative pressure collector is used to adsorb impurities generated during etching.

[0086] The quality inspection module in this embodiment is used to perform quality inspection on the battery after etching to verify the etching effect. The quality inspection includes testing at least one of the following: residual antireflection layer, substrate integrity, surface morphology, and contact performance. Specifically, the quality inspection module includes at least one of the following instruments: ellipsometry, scanning electron microscope and energy dispersive spectroscopy, four-probe microscopy, atomic force microscope, and IV microscopy.

[0087] The instrument includes a spectroscopic ellipsometry used to determine the distribution of residual antireflection layer through surface scanning; a scanning electron microscope used to observe the cross-sectional morphology of key points; and an energy dispersive spectroscopy (EDS) instrument used to verify the elemental composition of key points to detect the amount of residual antireflection layer. A four-probe tester is used to obtain the sheet resistance values ​​of etched and unetched areas to detect substrate integrity. An atomic force microscope is used to detect scratches or dents, and to detect the surface roughness of etched and unetched areas to detect surface morphology. An IV tester is used to perform IV performance tests before and after battery etching to detect contact performance.

[0088] The various instruments described above (including but not limited to industrial cameras, ultraviolet picosecond lasers, diffractive optical elements, scanning galvanometers, spectroscopic ellipsometers, scanning electron microscopes, energy dispersive spectrometers, four-probe testers, atomic force microscopes, IV testers, displacement platforms, industrial control computers, etc.) and their interconnections, as well as the internal structures and basic working principles of each component, are all implemented using existing technologies known in the art. The core innovation of this invention lies in combining the aforementioned components of the existing technology in a specific manner to execute the steps described above, thereby synergistically achieving the technical effect of precisely removing the antireflection layer 300 and improving substrate damage. Therefore, the specific circuit structures, internal optical configurations, detailed mechanical structures, and conventional control principles of each instrument component are not described in detail in this embodiment. Those skilled in the art, guided by the disclosure in this specification and combined with common knowledge in the art, can implement the technical solutions of this invention.

[0089] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0090] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for removing an antireflective layer from a solar cell, characterized in that, The solar cell includes an electrode (100) and an anti-reflection layer (300) covering the electrode (100), and the method includes: Step S1: Locate the contact area (400) between the electrode (100) and the test fixture. Step S2: In the contact area (400), the antireflection layer (300) is scanned and etched using an ultraviolet picosecond laser to expose the substrate covered by the antireflection layer (300); Step S3: During the etching process, inert gas is used to purge and clean the etched area; Step S4: After etching is completed, the battery is subjected to quality inspection to verify the etching effect. The quality inspection includes at least one of the following: antireflection layer residue detection, substrate integrity detection, surface morphology detection, and contact performance detection.

2. The method for removing the antireflective layer of a solar cell according to claim 1, characterized in that: Step S1 further includes: Step S11, acquire image data: Place the battery on the displacement platform and acquire a panoramic image of the battery as image data using an industrial camera; Step S12, extract contour features: use the algorithm model to extract the contour features of the electrode (100) from the image data; Step S13, analyze the deviation value: compare the spatial coordinates of the contour feature with the contact reference of the test fixture, and analyze the deviation value between the actual position of the current battery and the standard position. The deviation value includes the first deviation value in the length direction of the electrode (100) and the second deviation value in the width direction of the electrode (100). Step S14, position compensation: Move the displacement platform in the opposite direction of the deviation value, the amount of movement being equal to the absolute value of the deviation value, so that the outline of the electrode (100) is aligned with the contact reference, thereby positioning the contact area (400). Step S15, manual verification: Project the crosshair laser onto the battery surface and visually observe whether the center of the crosshair laser coincides with the center of the contact area (400); if the deviation exceeds the deviation verification threshold, then calibration is performed.

3. The method for removing the antireflective layer of a solar cell according to claim 2, characterized in that: Step S2 further includes: Step S21, set laser parameters: set the wavelength range to 266nm~355nm for ultraviolet picosecond laser, and select either constant energy scanning strategy or multi-level energy decreasing scanning strategy. Step S22, Spot shaping: First, a diffractive optical element is used to convert the Gaussian spot of the ultraviolet picosecond laser into a flat-top spot, and then a lens is used to focus the flat-top spot onto the contact area (400). Step S23, set the scanning path: control the ultraviolet picosecond laser to scan and etch the contact area (400) along the preset path, wherein the preset path is a path that scans the entire contact area (400) in a serpentine manner, or a path that first scans the edge of the pre-contact area in a circular manner, and then scans the inside of the pre-contact area in a serpentine manner. Step S24, Real-time monitoring: Use a monitoring camera to collect images of the etched area in real time, and use real-time grayscale value analysis to determine the etch progress. When the real-time grayscale value is stable at the grayscale threshold, stop the etch.

4. The method for removing the antireflective layer of a solar cell according to claim 3, characterized in that: In step S23, the contact area (400) includes a middle area (410) and two end areas (420), the two end areas (420) being located at both ends of the electrode (100) along its length and being arc-shaped; The middle region (410) is scanned at a first scanning speed, and the two end regions (420) are laser scanned at a second scanning speed, wherein the first scanning speed is greater than the second scanning speed.

5. The method for removing the antireflective layer of a solar cell according to claim 4, characterized in that: The antireflective layer (300) is magnesium fluoride, and the substrate covered by the antireflective layer (300) is tin; In step S22, the power ratio of the flat-top region of the flat-top spot is not less than 90%, the spot size is 50μm to 100μm, the spot overlap area is 30% to 50%, and the focal plane error does not exceed ±10μm. The grayscale threshold in step S24 is 130±5.

6. The method for removing the antireflective layer of a solar cell according to claim 5, characterized in that: The ultraviolet picosecond laser in step S21 has a wavelength of 355 nm and employs a multi-stage energy-decreasing scanning strategy, with the initial pulse energy density being 80 mJ / cm². 2 The etching rate was subsequently reduced to 50 mJ / cm², with 5 to 8 etching cycles. The preset path in step S23 is a serpentine scanning path of the entire contact area (400). During the entire serpentine scanning process, the first scanning speed is 2300mm / s to 2500mm / s, and the second scanning speed is 1100mm / s to 1300mm / s. or The ultraviolet picosecond laser in step S21 has a wavelength of 266 nm and adopts a constant energy scanning strategy. The single pulse energy density is 60 mJ / cm², and the etching number is 1 to 3 times. The preset path in step S23 is to first scan the edge of the pre-contact area in a circular motion, and then scan the inside of the pre-contact area in a serpentine motion. During the circular scanning process, the scanning speed is 500 mm / s. During the serpentine scanning process, the first scanning speed is 2300 mm / s to 2500 mm / s, and the second scanning speed is 1100 mm / s to 1300 mm / s.

7. The method for removing the antireflective layer of a solar cell according to any one of claims 1-6, characterized in that: Step S3 further includes: Step S31, set the purging parameters: use a nozzle to blow inert gas toward the etching area, the purging direction of the inert gas is at an angle of 10° to 65° with the laser scanning direction, and the purging pressure is 0.03MPa to 0.15MPa; Step 32, Residue Collection: A negative pressure collector is installed below the etched area to adsorb impurities generated during etching.

8. The method for removing the antireflective layer of a solar cell according to any one of claims 1-6, characterized in that: Step S4 includes at least one of the following sub-steps: Step S41, Antireflection layer residue detection: The distribution of the antireflection layer residue is determined by scanning the spectral ellipsometry, and the cross-sectional morphology and elemental analysis of key points are verified by scanning electron microscopy combined with energy dispersive spectroscopy. Finally, the continuous residue in the etched area and the total residue at the sampling points are used as dual judgment criteria. Step S42, Substrate integrity detection: A four-probe tester is used to obtain the sheet resistance values ​​of the etched area and the unetched area respectively. By analyzing the average value of the two values, the integrity of the substrate during the etching process is determined. Step S43, Surface morphology inspection: Atomic force microscopy is used to inspect scratches or depressions, and to inspect the surface roughness of the etched area and the unetched area to determine the impact of the etching process on the substrate surface. Step S44, Contact performance testing: By performing IV tests on the battery before and after etching, the changes in its series resistance and fill factor are obtained to determine the impact of the etching process on the contact performance.

9. The method for removing the antireflective layer of a solar cell according to any one of claims 1-6, characterized in that: It also includes a pretreatment step S0: cleaning and drying the battery to remove oil and dust from the battery surface; Step S0 further includes: Step S01, Cleaning the battery: A mixture of isopropanol and deionized water at a volume ratio of 1:3 is used as the cleaning solution. The equipment used includes an ultrasonic cleaner, and the cleaning time is 5 min to 8 min. Step S02, drying the battery: First, use an air knife to blow inert gas onto the battery surface at a wind speed of 10m / s to 15m / s and a temperature of 22℃ to 26℃; then use a vacuum drying oven to dry the moisture content on the battery surface to no more than 0.1mg / cm², with a vacuum degree of less than 1Pa, a drying temperature of 35℃ to 45℃, and a drying time of 30min to 40min.

10. A device for removing the antireflective layer of a solar cell, characterized in that, include: A positioning module is used to position the contact area (400) between the electrode (100) of the battery and the test fixture. A laser etching module is used to scan and etch the antireflection layer (300) in the contact area (400) using an ultraviolet picosecond laser to expose the substrate covered by the antireflection layer (300); The purging and cleaning module is used to purge and clean the etched area with inert gas during the etching process; as well as The quality inspection module is used to perform quality inspection on the battery after etching to verify the etching effect. The quality inspection includes the inspection of at least one of the following: residual amount of antireflection layer, substrate integrity, surface morphology and contact performance. The positioning module includes: A displacement platform for supporting and moving the battery; An industrial camera is used to acquire image data of the battery; an image processing unit is used to acquire image data of the battery and extract the contour features of the electrodes (100) from the image data using an algorithm model; An image processing unit is used to extract the contour features of the electrode (100) from the image data using an algorithm model; The deviation analysis unit is used to compare the contour features with the contact reference of the test fixture in spatial coordinates and analyze the deviation value between the actual position of the current battery and the standard position. A controller is configured to control the movement of the displacement platform based on the deviation value, so that the contour edge of the electrode (100) is aligned with the contact reference; and A laser line projector is used to emit a crosshair laser and project it onto the surface of the battery for manual verification of positioning accuracy. The laser etching module includes: Ultraviolet picosecond laser, used to generate ultraviolet picosecond laser; The optical path shaping unit includes a diffractive optical element for converting a Gaussian spot into a flat-top spot, and a lens for focusing the flat-top spot onto the contact area (400). A scanning galvanometer is used to control the ultraviolet picosecond laser to scan and etch the contact area (400) along a preset path; and A monitoring camera is used to acquire images of the etched area in real time and to determine the etching progress through real-time grayscale value analysis. The purging and cleaning module includes: Nozzles are used to blow inert gas toward the etched area; and Negative pressure collector is used to adsorb impurities generated during etching; The quality inspection module includes an instrument for at least one of the following tests: Spectroscopic ellipsometry, scanning electron microscope and energy dispersive spectroscopy are used to detect the amount of antireflection layer residue; A four-probe tester is used to perform substrate integrity testing. Atomic force microscopy is used to perform surface morphology inspection; and The IV tester is used to perform contact performance testing.

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