A rapid test method for solar cell contact resistance based on TLM

Abstract

This application relates to the field of photovoltaic device manufacturing and testing technology, specifically disclosing a rapid testing method for the contact resistance of solar cells based on TLM (Transmission Line Model). To address the problem of large fluctuations and numerous outliers in data measured by domestically produced equipment, the method includes: S1, Sample Preparation: Using a dicing machine, the main grids of the solar cell are removed, leaving the fine grids, to prepare strip-shaped test samples, which are then fixed on a testing platform; S2, Probe Matching and Testing: Based on the fine grid spacing of the strip-shaped test samples, a matching probe model is selected, and multiple fixed strip-shaped test samples are subjected to transmission line model testing to obtain contact resistance and resistivity data; S3, Outlier Data Processing: The dataset obtained in S2 undergoes two-level filtering: significantly large outlier data is deleted; the remaining data is sorted and a trend chart is plotted, deleting step-like jump points that deviate from the overall gradual upward trend. This application effectively solves the core pain point of large data fluctuations and numerous outliers in domestically produced equipment.

Description

Technical Field

[0001] This application relates to the field of photovoltaic device manufacturing and testing technology, and in particular to a rapid testing method for the contact resistance of solar cells based on TLM. Background Technology

[0002] As a clean and efficient renewable energy source, the conversion efficiency and long-term reliability of solar cells are core to the industry's development. In cell manufacturing, the ohmic contact quality between the metal electrodes (especially the fine grid) and the silicon substrate is crucial. Excessive contact resistance significantly increases series resistance, leading to a decrease in fill factor and conversion efficiency. Therefore, accurate assessment of contact resistance is an indispensable part of production process monitoring and quality control.

[0003] The Transmission Line Model (TLM) is currently the industry standard method for evaluating specific contact resistivity (ρc). However, traditional TLM testing methods face significant challenges in practical applications, especially when testing back-contact (such as PERC, TOPCon) or local contact batteries: First, the process is complex: test samples with specific electrode patterns need to be specially prepared, and the process differs from the actual battery manufacturing process, resulting in test results that cannot accurately reflect the performance of mass-produced batteries; second, the samples are not representative: the test structure differs from the complete grid design of real batteries, affecting the accuracy of the evaluation.

[0004] In terms of testing equipment, there are two main options in the market: imported equipment and domestic equipment. Imported equipment (such as the German PV-Tools TLM-SCAN) has mature technology, robust algorithms, and good data repeatability, but it is extremely expensive (about 2-3 times that of domestic equipment), and the probe procurement cycle is long (2-3 months), with slow after-sales service response and high costs.

[0005] To reduce testing costs and quickly respond to the ever-changing testing needs of future solar cell grids, domestically produced TLM equipment is the best choice. However, the immature technology of domestically produced equipment, large data fluctuations, and a large number of abnormal data urgently need to be addressed. Summary of the Invention

[0006] To reduce the problem of large fluctuations and numerous abnormal data obtained from domestically produced equipment, this application provides a rapid testing method for solar cell contact resistance based on TLM.

[0007] Firstly, this application provides a rapid testing method for the contact resistance of solar cells based on TLM, employing the following technical solution:

[0008] A rapid testing method for the contact resistance of solar cells based on TLM includes the following steps:

[0009] S1. Sample preparation: The main grid of the complete solar cell is removed using a dicing machine, leaving the fine grid to prepare a strip-shaped test sample; multiple strip-shaped test samples are fixed side by side on the test platform with the fine grids aligned.

[0010] S2. Probe matching and testing: Based on the fine grid spacing of the strip test sample, select a matching probe model from a set of probes with fixed spacing; use the selected probe to perform automated transmission line model testing on multiple fixed strip test samples to obtain the contact resistance and resistivity data of each fine grid on each sample.

[0011] S3. Abnormal data processing: Perform two-level filtering on the dataset obtained in S2: First, delete obviously large abnormal data based on process experience thresholds;

[0012] Next, the remaining data is sorted and a trend chart is drawn. Data with step-like jump points that deviate from the overall gentle upward trend are deleted to obtain the final set of valid test data.

[0013] Furthermore, in S1, the specific steps of sample preparation include: adjusting the laser parameters of the scribing machine to the optimal value, programming to scribing off the main grid portion of the battery cell to obtain a strip-shaped test sample with a width of 5-10 mm; when fixing, ensuring that all strip-shaped test samples are close to the upper reference edge and the left reference edge of the test platform, so that the fine grid pattern of all samples is in the same position on the two-dimensional plane.

[0014] Furthermore, in S2, probe matching is performed using a lookup table. The lookup table defines the range of sample grid spacing that is compatible with probe models with different fixed spacings. The matching rule is that the absolute value of the difference between the probe spacing and the sample grid spacing is not greater than 0.025 mm.

[0015] Furthermore, the probe spacing includes one or more of the following: 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1.0mm, and 1.05mm.

[0016] Furthermore, in S3, the specific criteria for the first-level screening are: deleting data points with a resistivity greater than 6 mΩ·cm².

[0017] Furthermore, in S3, the specific steps of the second-level screening are as follows: sort the data after the first-level screening according to the measurement order or numerical value, and draw a scatter plot of the contact resistance or resistivity value.

[0018] Identify single or multiple consecutive data points in the graph that form a significant vertical drop from the preceding and following data points and disrupt the gradual upward trend of the data, and delete them as step-like abrupt change points.

[0019] Furthermore, in S3, the specific steps of the second-level screening also include: sorting the data after the first-level screening according to the measurement order or numerical size, and drawing a scatter plot of the sheet resistance value.

[0020] Identify single or multiple consecutive data points in the graph that form a significant vertical drop from the preceding and following data points and disrupt the gradual upward trend of the data, and delete them as step-like abrupt change points.

[0021] Furthermore, the strip-shaped test sample prepared in S1 has a width of 6 mm and a preparation tolerance of ±0.03 mm.

[0022] Furthermore, the second-level screening in S3 specifically involves: automatically drawing a scatter plot of contact resistance and / or sheet resistance values ​​using software, with the data point number as the horizontal axis, and automatically identifying one or more consecutive data points in the plot that form a significant vertical drop with the preceding and following data points and disrupt the overall gentle upward trend as step-like jump points for deletion.

[0023] This application also provides a test sample preparation system for implementing the method according to any one of claims 1-9, comprising:

[0024] The dicing module is configured to precisely remove the main grid from a complete solar cell based on the input program and laser parameters, forming strip-shaped test samples;

[0025] The positioning and fixing module has an upper reference edge and a left reference edge that are perpendicular to each other. It is configured to accommodate multiple strip-shaped test samples and to bring the two ends of the sample strips close to the upper reference edge and the left reference edge, thereby aligning and fixing the fine grid pattern of all samples.

[0026] In summary, this application includes at least one of the following beneficial technical effects:

[0027] 1. By fully leveraging the advantages of domestically produced equipment—low ​​cost, fast probe supply, and timely service response—and by innovating methods to compensate for its algorithmic shortcomings, a high-performance-price ratio testing solution has been achieved, significantly reducing the testing and time costs for enterprises.

[0028] 2. Standardized sample preparation and clamping methods ensure the consistency of test samples with the fine grid process of mass-produced batteries, improving the representativeness of the tests. Systematic probe matching and alignment-based automated testing greatly reduce alignment difficulty and human error, improving test repeatability.

[0029] 3. The two-level abnormal data screening method can effectively filter out most of the random fluctuations and abnormal data generated by domestic equipment, extract stable and true contact resistance information from the messy data, and make the reliability of the test results of domestic equipment close to that of imported equipment.

[0030] 4. By using the "probe-grid spacing matching table" strategy, it can quickly respond to the ever-changing grid spacing requirements in battery R&D. Only the corresponding probe needs to be replaced, without changing the core testing method. It is highly flexible and particularly suitable for the rapid testing needs of R&D and diversified production lines. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the overall process of the testing method in this application;

[0033] Figure 2 This is a scatter plot of the contact resistance of Sample 1 and Sample 2 in the embodiments of this application;

[0034] Figure 3 This is a scatter plot of the sheet resistance of Sample 1 and Sample 2 in the embodiments of this application. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. Therefore, the detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to represent selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0036] The following combination Figures 1-3 This application will be described in further detail.

[0037] This application discloses a rapid testing method for the contact resistance of solar cells based on TLM, referring to... Figure 1 This includes the following steps:

[0038] S1. Sample preparation: Using a dicing machine, based on the fine grid pattern of the target solar cell, the laser frequency and power are programmed and adjusted to the optimal level to precisely remove the main grid electrodes on the solar cell, preparing a strip-shaped test sample with uniform width, which is between 5-10 mm wide.

[0039] In this embodiment, a mass-produced monocrystalline silicon Topcon solar cell is used as an example. The cell size is 183mm × 183mm, with 16 main grids (16BB) and a fine grid spacing of 0.9mm. The testing equipment used is the solar cell grid TLM contact resistivity analyzer from Aisen Intelligent Technology Co., Ltd.

[0040] Using the dicing machine's accompanying software, the cutting path was set parallel to the main grid direction, with a cutting width of 6.00 mm, to cut the solar cell into several independent strip samples. After cutting, the main grid was completely removed, resulting in sample strips with a width of (6.00±0.03) mm and a length of approximately 183 mm. Only the complete and undamaged mass-produced fine grid pattern was retained on each sample, with the fine grid direction parallel to the short side of the sample strip.

[0041] Five cut samples were randomly selected from a number of samples. Debris and contaminants were blown off the samples with an air gun, and then placed on clean filter paper for later use.

[0042] Place five samples side-by-side in the center of the sample stage. First, gently push the entire row of samples with your fingers until their long edges are tightly aligned with the precision-machined upper positioning edge on the sample stage, which serves as a reference. Then, maintaining this position, push the samples again until their end faces on the same side are tightly aligned with the left positioning edge, which is perpendicular to the upper positioning edge. Ensure that each fine grid on the five samples is strictly aligned in the two-dimensional plane coordinate system (XY direction).

[0043] S2. Probe Matching and Testing: Three of the five samples were measured using a measuring microscope, and the average value was taken to obtain an actual spacing of 0.898 mm. After determining the fine grid spacing, the corresponding probe spacing was determined by referring to the "Probe-Fine Grid Spacing Matching Reference Table" formulated in this application (see Table 1).

[0044] Probe spacing / mm 0.5 0.55 0.6 0.65 Sample fine grid spacing / mm 0.475-0.525 0.525-0.575 0.575-0.625 0.625-0.675 Probe spacing / mm 0.7 0.75 0.8 0.85 Sample fine grid spacing / mm 0.675-0.725 0.725-0.775 0.775-0.825 0.825-0.875 Probe spacing / mm 0.9 0.95 1 1.05 Sample fine grid spacing / mm 0.875-0.925 0.925-0.975 0.975-1.025 1.025-1.075

[0045] Table 1. Probe-Grid Spacing Matching Comparison Table

[0046] According to the "Probe-Fine Grating Spacing Matching Table", 0.898mm falls within the range of "0.875-0.925mm". Based on the matching principle that "the absolute value of the difference between the probe fixed spacing and the sample fine grating spacing is not greater than 0.025mm", a standard four-probe assembly with a probe fixed spacing S=0.9mm is selected.

[0047] Install the selected probe onto the probe holder of the tester, start the test software, and perform automatic sequence testing. The test logic is as follows:

[0048] The program first performs TLM measurement on the first fine grid of sample 1 at the starting coordinate point (the four probes apply current and measure voltage at this point, and then the probe group moves along the direction of the fine grid in steps of 0.9 mm, repeats the measurement at different spacing points, and finally fits and calculates the contact resistance Rc and sheet resistance Rsh of the fine grid).

[0049] Once completed, the sample stage automatically moves one sample strip width (6.00 mm) in the Y direction. Since the samples are precisely aligned, the probe assembly will automatically and accurately fall on the same relative position of the first fine grid of sample 2 without any visual alignment.

[0050] Repeat the above measurements. Test all 5 samples on the first fine grid in sequence.

[0051] Then, the sample stage returns to its initial position in the Y direction and moves by a set step in the X direction (for example, to jump to the position of the next fine grid to be tested), and begins testing the second fine grid of the five samples.

[0052] In this embodiment, each sample is tested with 20 representative fine grids, and the corresponding grid line numbers are: 1, 6, 11, 16, 26, 31, 36, 41, 46, 51, 56, 61, 66, 71, 76, 81, 86, 91, 93.

[0053]

[0054] Table 2 Test data for Sample 1 and Sample 2

[0055] S3. Abnormal Data Processing: After the test is completed, the device outputs a data table. In this embodiment, the data measured by sample 1 and sample 2 are used for analysis (as shown in Table 2). In the above data, sample 1 and sample 2 each have 20 measurement points. However, due to the equipment used, some test points are skipped because no data was measured, such as grid lines 51 and 56 of sample 1 and grid lines 56 and 61 of sample 2.

[0056] The dataset obtained from S2 is subjected to two levels of filtering:

[0057] First-level screening: Based on Topcon's long-term experience in the contact between battery silver paste and the n+ emitter, the normal resistivity is typically distributed in the range of 1.0–6.0 mΩ·cm². Resistivity > 6.0 mΩ·cm² usually indicates poor contact, inaccurate probe insertion, or measurement malfunction. Therefore, the first-level filtering threshold is set as resistivity > 6.0 mΩ·cm².

[0058] Delete all rows in Table 2 with resistivity (mΩ·cm²) greater than 6.0. For example, grid line 1 (6.42) and grid line 16 (12.01) of sample 1, and grid line 11 (15.72) and grid line 16 (15.17) of sample 2 are all removed in this round.

[0059] Sample 1 had 8 gate line data deleted, leaving 10 gate line data; Sample 2 had 6 gate line data deleted, leaving 12 gate line data.

[0060] Second-level screening: Sort the data of sample 1 and sample 2 after the first-level screening respectively to generate the contact resistance table of sample 1 (Table 3), the contact resistance table of sample 2 (Table 4), the sheet resistance table of sample 1 (Table 5), and the sheet resistance table of sample 2 (Table 6).

[0061]

[0062] Table 3 Contact Resistance of Sample 1

[0063]

[0064] Table 4 Contact Resistance of Sample 2

[0065]

[0066] Table 5 Shear resistance of sample 1

[0067]

[0068] Table 6 Shear resistance of sample 2

[0069] Based on Tables 3 and 4, using the data point number as the x-axis and the "contact resistance" value as the y-axis, the software automatically plotted a scatter plot of the contact resistance for Sample 1 and Sample 2 (refer to Table 4). Figure 2 Since the data trends of contact resistance and resistivity are consistent, only one scatter plot needs to be drawn.

[0070] Based on Tables 5 and 6, plot the sheet resistance scatter plots of Sample 1 and Sample 2 with the data point number as the x-axis and the sheet resistance value as the y-axis (refer to Table 6). Figure 3 ).

[0071] Reference Figure 2Using the data point number as the x-axis, the system automatically identifies and deletes single or multiple consecutive data points in the graph that form a significant vertical drop from the preceding and following data points, disrupting the overall gentle upward trend, as step-like jump points. Observing the data trends of the contact resistance of Sample 1 and Sample 2, the data of Sample 1 shows a slow upward trend, while the data point with serial number 1 in Sample 2 forms a clear "upward step" compared to the several consecutive data points in the 3.0-4.0Ω range that follow. This jump is usually caused by a slight slippage or contamination at the moment of probe contact at that specific measurement point. Therefore, the grid line corresponding to serial number 1 is identified and the jump point is deleted (Sample 2, grid line 51).

[0072] Reference Figure 3 Observe the data trends of sheet resistance for samples 1 and 2. The 10th data point in sample 1 shows a sudden increase, therefore the point with index 10 in sample 1 (sample 1, grid line 11) is deleted. In sample 2, the point with index 11 shows a sudden increase, therefore the point with index 11 is deleted (sample 2, grid line 26). The point with index 12 shows a sudden increase relative to the point with index 10, therefore the point with index 12 is deleted (sample 2, grid line 51).

[0073] In the second-level screening, grid line 11 was removed from sample 1, leaving 9 grid line data points, and grid line 51 was removed from sample 2, leaving 11 grid line data points. After the two-level screening, the volatility of the remaining dataset was significantly reduced, and the data distribution became more concentrated and reasonable.

[0074] The average contact resistance of the nine grid lines in sample 1 is approximately 3.54 Ω, the average sheet resistance is approximately 378.5 Ω / sq, and the average resistivity is approximately 4.46 mΩ·cm².

[0075] The average contact resistance of the 11 grid lines in sample 2 was calculated to be approximately 3.4 Ω, the average sheet resistance was approximately 377.3 Ω / sq, and the average resistivity was approximately 4.2 mΩ·cm².

[0076] The average values ​​of Sample 1 and Sample 2 were calculated, and it was found that the contact resistance of the monocrystalline silicon Topcon solar cell in this embodiment was approximately 3.47Ω, the sheet resistance was approximately 377.9Ω / sq, and the resistivity was approximately 4.33mΩ·cm².

[0077] Before the data was filtered, the average contact resistance of all 36 grid lines was approximately 4.7Ω, the average sheet resistance was approximately 377.38Ω / sq, and the average resistivity was approximately 6.05mΩ·cm².

[0078] To verify the effectiveness of this method, a reference sample from the same batch of batteries was tested using a PV-Tools TLM-SCAN instrument imported from Germany. The average contact resistance measured by the imported instrument was 2.96Ω, the sheet resistance was approximately 386.2Ω / sq, and the average resistivity was 3.64mΩ·cm².

[0079] The comparison showed that the contact resistance data obtained after secondary screening was closer to the data measured by imported equipment. This proves that the method can effectively identify and filter out significant outliers introduced by factors such as equipment fluctuations and poor contact, making the test results closer to the true level of the process.

[0080] Despite the limitations of the inherent hardware and basic algorithm accuracy of domestically produced equipment, the test results obtained by the method of this invention (resistivity ≈ 4.33 mΩ·cm²) are on the same order of magnitude as the test results of the benchmark equipment imported from Germany (resistivity ≈ 3.64 mΩ·cm²), and the deviation is within a reasonable range.

[0081] In summary, this application addresses the core pain points of large data fluctuations and numerous outliers by providing a complete and replicable process methodology without modifying the hardware of domestically produced equipment or significantly increasing costs. This enables users to obtain test data that meets the requirements of process development and quality control at a cost far lower than that of imported equipment (approximately 1 / 3 to 1 / 2), achieving the established goals of reducing testing costs and rapidly responding to changing needs.

[0082] This embodiment also discloses a test sample preparation and positioning system for implementing the above method, including a scribing module and a positioning and fixing module. The positioning and fixing module has high-precision mutually perpendicular reference edges, including a mutually perpendicular upper reference edge and a left reference edge, for achieving rapid and accurate alignment and fixing of the sample.

[0083] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A rapid testing method for the contact resistance of solar cells based on TLM, characterized in that, Includes the following steps: S1. Sample preparation: The main grid of the complete solar cell is removed using a dicing machine, leaving the fine grid to prepare a strip-shaped test sample; multiple strip-shaped test samples are fixed side by side on the test platform with the fine grids aligned. S2. Probe matching and testing: Based on the fine grid spacing of the strip test sample, select a matching probe model from a set of probes with fixed spacing; use the selected probe to perform automated transmission line model testing on multiple fixed strip test samples to obtain the contact resistance and resistivity data of each fine grid on each sample. S3. Abnormal data processing: Perform two-level filtering on the dataset obtained in S2: First, delete obviously large abnormal data based on process experience thresholds; Next, the remaining data is sorted and a trend chart is drawn. Data with step-like jump points that deviate from the overall gentle upward trend are deleted to obtain the final set of valid test data.

2. The rapid testing method for solar cell contact resistance based on TLM according to claim 1, characterized in that, In step S1, the specific steps of sample preparation include: adjusting the laser parameters of the scribing machine to the optimal value, programming to scribing off the main grid portion of the battery cell to obtain a strip-shaped test sample with a width of 5-10 mm; when fixing, ensuring that all strip-shaped test samples are close to the upper reference edge and the left reference edge of the test platform, so that the fine grid pattern of all samples is in the same position on the two-dimensional plane.

3. The rapid testing method for solar cell contact resistance based on TLM according to claim 1, characterized in that, In step S2, probe matching is performed using a lookup table. The lookup table defines the range of sample grid spacing that is compatible with probe models with different fixed spacings. The matching rule is that the absolute value of the difference between the probe spacing and the sample grid spacing is not greater than 0.025 mm.

4. The rapid testing method for solar cell contact resistance based on TLM according to claim 3, characterized in that, The probe spacing includes one or more of the following: 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1.0mm, and 1.05mm.

5. The rapid testing method for solar cell contact resistance based on TLM according to claim 1, characterized in that, In S3, the specific criteria for the first-level screening are: to delete data points with resistivity greater than 6 mΩ·cm².

6. The rapid testing method for solar cell contact resistance based on TLM according to claim 5, characterized in that, In S3, the specific steps of the second-level screening are as follows: sort the data after the first-level screening according to the measurement order or the value size, and draw a scatter plot of the contact resistance or resistivity value. Identify single or multiple consecutive data points in the graph that form a significant vertical drop from the preceding and following data points and disrupt the gradual upward trend of the data, and delete them as step-like abrupt change points.

7. The rapid testing method for solar cell contact resistance based on TLM according to claim 5, characterized in that, In S3, the specific steps of the second-level screening also include: sorting the data after the first-level screening according to the measurement order or the size of the values, and drawing a scatter plot of the sheet resistance values. Identify single or multiple consecutive data points in the graph that form a significant vertical drop from the preceding and following data points and disrupt the gradual upward trend of the data, and delete them as step-like abrupt change points.

8. The rapid testing method for solar cell contact resistance based on TLM according to claim 1, characterized in that, The strip-shaped test sample prepared in S1 has a width of 6 mm and a preparation tolerance of ±0.03 mm.

9. The rapid testing method for solar cell contact resistance based on TLM according to claim 1, characterized in that, The second-level screening in S3 specifically involves: automatically drawing a scatter plot of contact resistance and / or sheet resistance values ​​using software, with the data point number as the horizontal axis, and automatically identifying one or more consecutive data points in the plot that form a significant vertical drop with the preceding and following data points and disrupt the overall gentle upward trend as step-like jump points for deletion.

10. A test sample preparation system for implementing the method according to any one of claims 1-9, characterized in that, include: The dicing module is configured to precisely remove the main grid from a complete solar cell based on the input program and laser parameters, forming strip-shaped test samples; The positioning and fixing module has an upper reference edge and a left reference edge that are perpendicular to each other. It is configured to accommodate multiple strip-shaped test samples and to bring the two ends of the sample strips close to the upper reference edge and the left reference edge, thereby aligning and fixing the fine grid pattern of all samples.

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