Performance testing methods, devices, and storage media for photovoltaic cells

Abstract

This application relates to a performance testing method, apparatus, and storage medium for photovoltaic cells. The testing method involves electroluminescence detection of the test sample to obtain a first electroluminescence image; multiple consecutive temperature shock tests are performed on the test sample; the temperature difference of a single temperature shock test is greater than 130°C; after multiple temperature shock tests, electroluminescence detection is performed on the test sample to obtain a second electroluminescence image; based on the first and second electroluminescence images, the temperature shock resistance of the solder joints of the cells in the test sample is evaluated; thereby accumulating equivalent damage in fewer cycles, reducing testing costs, shortening the duration of a single test, compressing the testing cycle, and improving testing feedback efficiency, which can meet the higher requirements for testing efficiency in the research and development iteration of new processes and materials.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a method, apparatus, and storage medium for testing the performance of photovoltaic cells. Background Technology

[0002] Photovoltaic modules are the components of a photovoltaic (PV) power generation system, and their long-term reliability affects the overall system's power generation efficiency and lifespan. In outdoor operating environments, PV modules are subjected to drastic temperature changes; during the day, under direct sunlight, module temperatures can reach above 70°C, while at night, ambient temperatures can drop below -30°C. These alternating high and low temperature shocks pose a severe challenge to the various connection points of the PV modules.

[0003] In photovoltaic modules, the metallized electrodes of the solar cells and the photovoltaic solder ribbons are electrically connected by welding. The silicon solar cells, metallized electrodes, solder, and solder ribbons have significantly different coefficients of thermal expansion. During temperature cycling, mechanical stress is generated at the welding interface. This stress accumulation can lead to solder joint cracking, microcracks in the solar cells, and increased series resistance, ultimately causing module power degradation or even failure. Summary of the Invention

[0004] Therefore, it is necessary to provide a performance testing method, apparatus, and storage medium for photovoltaic cells to address the aforementioned technical problems.

[0005] Firstly, this application provides a performance testing method for photovoltaic cells, including:

[0006] Prepare a test sample, the test sample comprising at least two battery cells connected in series by solder strips;

[0007] Electroluminescence detection was performed on the test sample to obtain a first electroluminescence image;

[0008] The test sample is subjected to multiple consecutive temperature shock tests; wherein a single temperature shock test includes a cooling phase from a first temperature to a second temperature, a second temperature holding phase, a heating phase from the second temperature to the first temperature, and a first temperature holding phase; wherein the temperature difference between the first temperature and the second temperature is greater than 130°C.

[0009] After completing multiple temperature shock tests, electroluminescence detection was performed on the test sample to obtain a second electroluminescence image;

[0010] Based on the first electroluminescent image and the second electroluminescent image, the temperature shock resistance of the welding points of the battery cells in the test sample is evaluated.

[0011] In one embodiment, evaluating the temperature shock resistance of the weld joints of the battery cells in the test sample based on the first electroluminescent image and the second electroluminescent image includes:

[0012] Comparing the first electroluminescent image with the second electroluminescent image, if a local discoloration area appears in the second electroluminescent image, the discoloration area corresponds to the welding point;

[0013] Measure the first pull-out force of the discolored area and the second pull-out force of the weld point in the undiscolored area of ​​the test sample;

[0014] Compare the difference rate between the first pull-out force and the second pull-out force. If the difference rate between the first pull-out force and the second pull-out force exceeds a set threshold, it is determined that the welding point of the test sample has become abnormal after multiple temperature shock tests.

[0015] In one embodiment, in the temperature shock test, the first temperature is set between 100°C and 110°C, and the second temperature is set between -35°C and -45°C; and the total duration of multiple temperature shock tests is less than 48 hours.

[0016] In one embodiment, during the temperature shock test, the first temperature is 105°C and the second temperature is -40°C; the temperature change rate during the cooling phase is less than 100°C / hour; and the temperature change rate during the heating phase is less than 100°C / hour.

[0017] In one embodiment, the temperature shock test is performed 4 to 20 times.

[0018] In one embodiment, the test sample comprises 3-6 battery cells interconnected in series by solder strips, and busbars are welded to both ends of the test sample.

[0019] In one embodiment, when performing electroluminescence detection on the test sample, a forward test current with the same direction as the PN junction of the battery cell is passed into the busbar of the battery cell, and the magnitude of the forward test current is between 0.5 and 1.5 times the short-circuit current of the battery cell.

[0020] In one embodiment, it includes:

[0021] Prepare a first test sample and a second test sample, wherein the first test sample and the second test sample differ in at least one of the following: cell type or welding process;

[0022] Electroluminescence detection is performed on the first test sample to obtain a first electroluminescence image of the first test sample; electroluminescence detection is performed on the second test sample to obtain a first electroluminescence image of the second test sample;

[0023] The first test sample and the second test sample were subjected to multiple consecutive temperature shock tests under the same conditions.

[0024] Electroluminescence detection is performed on the first test sample to obtain a second electroluminescence image of the first test sample; electroluminescence detection is performed on the second test sample to obtain a second electroluminescence image of the second test sample;

[0025] The temperature shock resistance of the solder joints of the battery cells in the first test sample and the temperature shock resistance of the solder joints of the battery cells in the second test sample are evaluated, and the evaluation results of the first test sample and the second test sample are compared.

[0026] Secondly, this application provides a performance testing device for photovoltaic cells, including an electroluminescence detection module, a temperature testing module, and an evaluation module:

[0027] The electroluminescence detection module is used to perform electroluminescence detection on the test sample to obtain a first electroluminescence image; the test sample includes at least two battery cells connected in series by solder strips.

[0028] The temperature testing module is used to perform multiple consecutive temperature shock tests on the test sample; wherein, a single temperature shock test includes a cooling phase from a first temperature to a second temperature, a second temperature holding phase, a heating phase from the second temperature to the first temperature, and a first temperature holding phase.

[0029] The electroluminescence detection module is also used to perform electroluminescence detection on the test sample after completing multiple temperature shock tests to obtain a second electroluminescence image.

[0030] The evaluation module is used to evaluate the temperature shock resistance of the welding points of the battery cells in the test sample based on the first electroluminescent image and the second electroluminescent image.

[0031] Thirdly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described in the first aspect.

[0032] The aforementioned photovoltaic cell performance testing method, apparatus, and storage medium perform electroluminescence detection on the test sample to obtain a first electroluminescence image; conduct multiple consecutive temperature shock tests on the test sample; the temperature difference of a single temperature shock test is greater than 130°C; after multiple temperature shock tests, perform electroluminescence detection on the test sample to obtain a second electroluminescence image; based on the first and second electroluminescence images, evaluate the temperature shock resistance of the welding points of the cells in the test sample. This application tests the test sample, which is smaller in size and has a smaller heat capacity. The temperature difference of a single temperature shock test is greater than 130°C, increasing the fatigue damage to the test sample from a single temperature shock test, thereby accumulating equivalent damage in fewer cycles. This reduces testing costs, shortens the single test time, compresses the test cycle, and improves test feedback efficiency, meeting the higher requirements for testing efficiency in the research and development iteration of new processes and materials. Simultaneously, the smaller size of the test sample allows for testing using a small temperature test chamber, reducing equipment investment costs and the complexity of test condition control, which is beneficial for improving test controllability and the accuracy of test results. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a flowchart illustrating a performance testing method for photovoltaic cells in one embodiment;

[0035] Figure 2 This is a schematic diagram of a test sample in one embodiment;

[0036] Figure 3 This is a first electroluminescence image of a test sample in one embodiment;

[0037] Figure 4 This is a second electroluminescence image of a test sample in one embodiment;

[0038] Figure 5 This is a flowchart illustrating a performance testing method for photovoltaic cells in another embodiment;

[0039] Figure 6 This is a structural block diagram of a photovoltaic cell performance testing device in one embodiment. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0041] In related technologies, high and low temperature cycling tests (TC tests) are conducted on photovoltaic modules to verify their ability to withstand temperature shocks. Complete photovoltaic modules are placed in a test chamber and subjected to repeated temperature cycles between -40℃ and +85℃, with each cycle lasting approximately 4 hours. The tests include TC200 (200 cycles, approximately 33 days) and TC400 (400 cycles, approximately 66 days).

[0042] However, the existing high and low temperature cycling tests have too long a testing cycle. A single TC200 test takes 33 days, and a TC400 test takes 66 days. The verification cycle for new processes and materials is forced to be extended, feedback is severely delayed, testing costs are high and space is occupied. Only a limited number of samples can be tested, which is difficult to meet the needs of rapid screening.

[0043] Therefore, there is an urgent need to develop a test method that can quickly evaluate the thermal shock resistance of battery cell welding points in order to shorten the test cycle, reduce test costs, and meet the needs of rapid screening and iteration in the R&D and production process.

[0044] Firstly, this application provides a performance testing method for photovoltaic cells, referring to... Figure 1 As shown, the performance testing method for photovoltaic cells includes the following steps:

[0045] Step S101: Prepare a test sample, which includes at least two solar cells connected in series by solder strips.

[0046] In this embodiment, refer to Figure 2 The test sample was produced by welding at least two solar cells from the same batch together using the same welding process. The number of solar cells and the overall area occupied by the test sample were much smaller than those of conventional photovoltaic modules.

[0047] In this embodiment, multiple test samples can be made using the same type of battery cell, or multiple different samples can be made using different battery cells, or multiple different samples can be made using different solder strips. Multiple samples can be tested together to improve test accuracy or to conduct comparative tests.

[0048] Step S102: Perform electroluminescence detection on the test sample to obtain the first electroluminescence image.

[0049] In this embodiment, the test sample is connected to a DC power supply, a test current is applied to the test sample, and then an infrared camera is used to photograph the test sample for reference. Figure 3 The first electroluminescence image of the test sample is obtained. The first electroluminescence image is then examined. If it is uniform and bright, without dark areas, dark lines, black spots, or other defects, it indicates that the initial welding quality of the sample is good and it can be used for subsequent testing. If the first electroluminescence image contains uneven dark areas, dark lines, black spots, or other defects, the corresponding test sample is discarded, and other test samples are selected for testing.

[0050] Step S103: Perform multiple consecutive temperature shock tests on the test sample; wherein, a single temperature shock test includes a cooling stage from the first temperature to the second temperature, a second temperature holding stage, a heating stage from the second temperature to the first temperature, and a first temperature holding stage; wherein, the temperature difference between the first temperature and the second temperature is greater than 130℃.

[0051] In this embodiment, the test sample that meets the test conditions is placed in a temperature test chamber and subjected to a temperature shock test. In this embodiment, the temperature difference of a single temperature shock test is increased to greater than 130°C, which increases the thermomechanical stress borne by the welding interface in each cycle, thereby accumulating the expected fatigue damage in fewer cycles and shortening the total time of the temperature shock test.

[0052] It is understood that the thermomechanical stress borne by the welding interface during temperature cycling is positively correlated with the impact temperature difference. In this embodiment, the temperature difference of a single temperature shock test is increased to more than 130°C. The thermomechanical stress borne by the sample in a single cycle test increases, the fatigue damage of the test sample increases, thereby shortening the total time of the temperature shock test.

[0053] Step S104: After completing multiple temperature shock tests, perform electroluminescence detection on the test sample to obtain a second electroluminescence image.

[0054] In this embodiment, after the temperature shock test is completed, the test sample is allowed to cool naturally to room temperature. The sample is then removed, and electroluminescence detection is performed on the test sample under the same conditions as in step S102, referring to… Figure 4 The second electroluminescence image after the test was obtained.

[0055] Step S105: Based on the first electroluminescence image and the second electroluminescence image, evaluate the temperature shock resistance of the welding points of the battery cells in the test sample.

[0056] Reference Figure 3 , Figure 4 As shown, the second electroluminescence image of the test sample is compared with the first electroluminescence image. Figure 3As shown, all weld point areas in the first electroluminescence image exhibit uniform and bright illumination, indicating good initial weld quality of the sample. Figure 4 As shown, if the second electroluminescence image shows obvious dark areas around the weld points, continuous dark bands along the weld ribbon direction, or a single cell with a significantly lower overall luminescence intensity than other cells, then a welding abnormality may exist at the corresponding location. Based on the abnormal areas appearing in the second electroluminescence image, the corresponding locations are marked on the test sample, and the cell and specific location of the abnormal point are recorded. Each abnormal weld point is then inspected individually; for example, a pull-out force test can be performed to determine whether the weld points in each abnormal area (dark area) became abnormal after the temperature shock test.

[0057] If the second electroluminescence image of the test sample has no abnormal areas, or if there are abnormal areas but the welding points corresponding to all abnormal areas in the second electroluminescence image pass the pull-out force test, then the temperature shock resistance test of the test sample is qualified; if there is one welding point in the second electroluminescence image of the test sample that fails the pull-out force test, then the temperature shock resistance test of the test sample is not qualified.

[0058] The aforementioned performance testing method for photovoltaic cells involves electroluminescence detection of the test sample to obtain a first electroluminescence image; multiple consecutive temperature shock tests are performed on the test sample; the temperature difference of a single temperature shock test is greater than 130°C; after multiple temperature shock tests, electroluminescence detection is performed on the test sample to obtain a second electroluminescence image; based on the first and second electroluminescence images, the temperature shock resistance of the welding points of the cells in the test sample is evaluated. This application tests the sample, which is smaller in size and has a smaller heat capacity. The temperature difference of a single temperature shock test is greater than 130°C, increasing the fatigue damage to the test sample from a single temperature shock test, thereby accumulating equivalent damage in fewer cycles. This reduces testing costs, shortens the single test duration, compresses the testing cycle, and improves testing feedback efficiency, meeting the higher requirements for testing efficiency in the research and development iteration of new processes and materials. Simultaneously, the smaller size of the test sample allows for testing using a small temperature testing chamber, reducing equipment investment costs and the complexity of test condition control, which is beneficial for improving test controllability and the accuracy of test results.

[0059] In one embodiment, the temperature shock resistance of the solder joints of the battery cells in the test sample is evaluated based on a first electroluminescent image and a second electroluminescent image, including:

[0060] Step S1051: Compare the first electroluminescent image with the second electroluminescent image. If a local discoloration area appears in the second electroluminescent image, the discoloration area corresponds to the welding point.

[0061] Reference Figure 3 , Figure 4 The second electroluminescence image of the test sample was compared with the first electroluminescence image to observe whether there were any image differences, with particular attention paid to the change in luminescence intensity at the connection between the main grid line and the solder ribbon of the solar cell. (Refer to...) Figure 4 As shown in the area within the middle bar, if a localized darkening, blackening, or banded dark area appears in the second electroluminescence image, and this area contrasts significantly with the corresponding normal luminescent area in the first image, then this location is determined to be a suspicious abnormal solder joint. Based on the location of the darkened area in the second electroluminescence image, the corresponding solder joint is marked on the test sample. For test samples with multiple cells connected in series, the cell number (Nth cell from left to right) and specific location (left solder joint, right solder joint, or middle solder joint) of the abnormal point should be accurately recorded.

[0062] Step S1052: Measure the first pull-out force of the discolored area and the second pull-out force of the weld point of the undiscolored area of ​​the test sample.

[0063] In this embodiment, the solder strip pull-out force test is performed on the marked suspicious abnormal solder joints. At the same time, the solder joints in the uncolored area (normal area) of the second electroluminescent image of the same test sample are selected as a control and the solder strip pull-out force test is performed.

[0064] A tensile tester can be used to pull the weld strip in the discolored area of ​​the test sample at a uniform speed in a 90° vertical direction, with the pulling speed controlled at 50±5 mm / min. The first pull-out force F1 of any suspected abnormal weld point should be recorded. Similarly, a tensile tester can be used to pull the weld strip in the undiscolored area at a uniform speed in a 90° vertical direction, with the pulling speed controlled at 50±5 mm / min. The second pull-out force F2 of any suspected control weld point should be recorded.

[0065] Step S1053: Compare the difference rate between the first pull-out force and the second pull-out force. If the difference rate between the first pull-out force and the second pull-out force exceeds the set threshold, it is determined that the welding point of the test sample has become abnormal after multiple temperature shock tests.

[0066] In this embodiment, the difference rate between the first pull-out force F1 and the second pull-out force F2 is calculated. If the difference rate between the first pull-out force and the second pull-out force is less than a set threshold, it is determined that the suspected abnormal welding point of the test sample has not shown any obvious abnormality after multiple temperature shock tests. The dark image may be caused by other factors (such as surface contamination, shooting angle, etc.). If the difference rate between the first pull-out force and the second pull-out force is greater than or equal to the set threshold, it is determined that the suspected abnormal welding point has become abnormal after the temperature shock test, indicating that the suspected abnormal welding point has insufficient resistance to temperature shock.

[0067] If no color-changing area appears in the second electroluminescent image, or if the difference rate between the first pull-out force and the second pull-out force of the suspected abnormal weld point in the second electroluminescent image and the color-changing area is less than a set threshold, the temperature shock resistance performance of the weld point of the battery cell in the test sample is qualified; if the difference rate between the first pull-out force and the second pull-out force is greater than or equal to the set threshold, the temperature shock resistance performance of the weld point of the battery cell in the test sample is unqualified.

[0068] For example, the threshold can be set to 30%. If the difference rate between the first pull-out force and the second pull-out force is less than the set threshold, the temperature shock resistance of the welding point of the battery cell in the test sample is qualified. If the difference rate between the first pull-out force and the second pull-out force is greater than or equal to 30%, the temperature shock resistance of the welding point of the battery cell in the test sample is unqualified.

[0069] It is understandable that in practical applications, the testing and evaluation standards can be adjusted, such as conducting multi-level evaluations and classifying the evaluation results into grades A, B, C, etc.

[0070] In one embodiment, during the temperature shock test, the first temperature is set between 100°C and 110°C, for example, the first temperature can be 100°C, 102°C, 104°C, 105°C, 107°C, 108°C, or 110°C; the second temperature is set between -35°C and -45°C, for example, the second temperature can be -35°C, -36°C, -38°C, -40°C, -42°C, -43°C, -44°C, or -45°C; and the total duration of multiple temperature shock tests is less than 48 hours.

[0071] In this embodiment, the duration of a single temperature shock test does not exceed 8 hours, for example, it can be 66-8 hours, and the duration of performing a complete temperature shock test on the test sample is less than 48 hours. This embodiment can complete the temperature shock test of the test sample within 2 working days, which greatly improves the testing efficiency.

[0072] In one embodiment, during the temperature shock test, the first temperature is 105°C and the second temperature is -40°C; the temperature change rate during the cooling phase is less than 100°C / hour; thus, during the temperature shock test, the temperature difference between the high and low temperatures is 145°C. The weld joint experiences high thermomechanical stress during the temperature cycle. Increasing the temperature difference can directly enhance the damage to the weld joint of the test sample in a single test, thereby achieving equivalent cumulative damage in fewer cycles, shortening the test cycle, and achieving a test cycle of less than 48 hours.

[0073] In this embodiment, the temperature change rate during the heating phase is less than 100°C / hour; in this embodiment, the temperature change rate during the cooling phase is less than 100°C / hour. This avoids excessively rapid temperature changes that could cause thermal stress cracks in the solar cell, ensuring that the failure mode remains concentrated at the weld interface rather than within the solar cell itself.

[0074] Furthermore, the temperature change rate during the heating and cooling phases is 85℃ / hour to 100℃ / hour. For example, the temperature change rate during the heating phase can be 85℃ / hour, 87℃ / hour, 88℃ / hour, 90℃ / hour, 92℃ / hour, 93℃ / hour, 95℃ / hour, 96.7℃ / hour, 97.8℃ / hour, 98℃ / hour, 99℃ / hour, or 100℃ / hour.

[0075] In one embodiment, the number of temperature shock tests is 4 to 20. For example, the number of temperature shock tests can be 4, 6, 8, 10, 12, 14, 15, 16, 18, or 20.

[0076] In one embodiment, the test sample is placed in a temperature test chamber. The initial temperature of the test sample is room temperature (approximately 25°C). Therefore, in the first temperature shock test, the temperature of the test sample is reduced from room temperature to -40°C at a cooling rate of 80°C / hour to 100°C / hour, and the first cooling phase takes 1 to 1.5 hours. The low temperature holding phase is maintained at -40°C for 1 to 2 hours. In the heating phase, the temperature is increased from -40°C to 105°C at a heating rate of 80°C / hour to 100°C / hour, taking 1.5 to 2.5 hours. The high temperature holding phase is maintained at 105°C for 1 to 2 hours, thus completing the first temperature shock test.

[0077] Then, the temperature was lowered from 105℃ to -40℃ at a rate of 80℃ / hour to 100℃ / hour, lasting 1.5 to 2.5 hours. The low-temperature holding phase was maintained at -40℃ for 1 to 2 hours. The heating phase was then raised from -40℃ to 105℃ at a rate of 80℃ / hour to 100℃ / hour, lasting 1.5 to 2.5 hours. The high-temperature holding phase was maintained at 105℃ for 1 to 2 hours, completing the second temperature shock test. Afterward, the same temperature shock test as the second temperature shock test was repeated until the test was completed.

[0078] In one embodiment, the test sample is placed in a temperature test chamber and eight re-temperature shock tests are performed as one test cycle.

[0079] First cycle: The sample temperature was lowered from room temperature (25°C) to -40°C over 1 hour at a cooling rate of 85°C / hour. The sample was then held at -40°C for 1 hour. The sample temperature was then raised from -40°C to 105°C over approximately 1.7 hours at a heating rate of 85°C / hour. The sample was held at 105°C for 1 hour. Total duration of the first cycle: approximately 4.7 hours.

[0080] Second cycle: The sample temperature was lowered from 105℃ to -40℃ at a cooling rate of 85℃ / hour, taking approximately 1.7 hours. It was then held at -40℃ for 1 hour. The sample temperature was then raised from -40℃ to 105℃ at a heating rate of 85℃ / hour, taking approximately 1.7 hours. It was then held at 105℃ for 1 hour. Total time: Approximately 5.4 hours.

[0081] The third through eighth cycles are the same as the second cycle, each lasting approximately 5.4 hours.

[0082] The total duration of a test cycle is approximately 44.6 hours, which is less than 48 hours (2 days). As can be seen, by setting the parameters above, the test cycle can be shortened to within 2 days.

[0083] In another embodiment, the test sample is placed in a temperature test chamber and nine re-temperature shock tests are performed as one test cycle.

[0084] First cycle: The sample temperature was lowered from room temperature (25°C) to -40°C in 0.7 hours at a cooling rate of 90°C / hour. It was then held at -40°C for 1 hour. The sample temperature was then raised from -40°C to 105°C in approximately 1.6 hours at a heating rate of 90°C / hour. It was then held at 105°C for 1 hour. Total duration of the first cycle: approximately 4.3 hours.

[0085] Second cycle: The sample temperature was lowered from 105℃ to -40℃ at a cooling rate of 90℃ / hour, taking approximately 1.6 hours. It was then held at -40℃ for 1 hour. The sample temperature was then raised from -40℃ to 105℃ at a heating rate of 90℃ / hour, taking approximately 1.6 hours. It was then held at 105℃ for 1 hour. Total time: approximately 5.2 hours.

[0086] The third through ninth cycles are the same as the second cycle, each lasting approximately 5.2 hours.

[0087] The total duration of nine cycles is approximately 46.2 hours, which is less than 48 hours (2 days). As can be seen, by setting the parameters above, the test cycle can be shortened to within 2 days.

[0088] In one embodiment, reference Figure 2 The test sample consists of 3-6 battery cells interconnected in series by solder ribbons, with busbars welded to both ends. In this embodiment, 3-6 battery cells are connected in series by solder ribbons to form a small battery string. Busbars are welded to both ends of the battery string to form a complete electrical circuit.

[0089] It is understandable that when the number of solar cells is 2 or less, although the test sample is small in size and has low heat capacity, it cannot simulate the stress transfer between multiple welding points. When the number of solar cells is more than 6, the size of the test sample is closer to that of a real photovoltaic module, the heat capacity is increased, the heating and cooling rate is slow, and the test cycle is long. In this embodiment, the test sample includes 3-6 solar cells, and the solder ribbon and the solar cell can form at least two intermediate welding points. The stress state is closer to the welding point in the middle of the real module. At the same time, the size of the test sample is smaller than that of a real photovoltaic module, the heat capacity of the test sample is reduced, the heating and cooling rate is fast, and the test cycle can be effectively shortened.

[0090] In one embodiment, when performing electroluminescence detection on the test sample, a forward test current with the same direction as the PN junction of the battery cell is passed into the busbar of the battery cell. The magnitude of the forward test current is between 0.5 and 1.5 times the short-circuit current Isc of the battery cell.

[0091] For example, the forward test current can be selected from multiple different current values ​​within the range of 0.5 to 1.5 times the short-circuit current Isc, depending on the testing purpose and sample characteristics, to test the sample. For instance, the forward test current can be set to 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5 times the short-circuit current Isc of the solar cell.

[0092] In one embodiment, reference Figure 5 The performance testing method for photovoltaic cells also includes the following steps:

[0093] Step S201: Prepare a first test sample and a second test sample, wherein the first test sample and the second test sample differ in at least one of the following: cell type or welding process.

[0094] In this embodiment, at least two test samples are prepared: a first test sample and a second test sample. The first test sample and the second test sample differ in at least one of the following: cell type or welding process. For example, the first test sample and the second test sample may have different cell types, welding process parameters, solder ribbon materials, or flux. In one example, the first test sample uses TOPCon cells, the second test sample uses PERC cells, and the first and second test samples have the same welding process and solder ribbons. In another example, the first and second test samples use the same cell types but different solder ribbon materials.

[0095] In this embodiment, both the first test sample and the second test sample are series-connected battery strings consisting of four battery cells, with busbars welded to both ends.

[0096] In this embodiment, multiple first test samples and multiple second test samples are prepared and used together for testing to increase the sample size and eliminate the influence of random factors.

[0097] Step S202: Perform electroluminescence detection on the first test sample to obtain the first electroluminescence image of the first test sample; perform electroluminescence detection on the second test sample to obtain the first electroluminescence image of the second test sample.

[0098] Connect the first test sample and the second test sample to a DC power supply respectively, and apply a forward test current to the first test sample and the second test sample respectively, with the current being 1.0 times the short-circuit current Isc of the battery cell.

[0099] Electroluminescence detection was performed on the first test sample to obtain the first electroluminescence image of the first test sample; electroluminescence detection was performed on the second test sample to obtain the first electroluminescence image of the second test sample.

[0100] The first electroluminescence images of the first and second test samples should be uniform, bright, and without abnormalities to ensure that subsequent performance differences stem from post-test changes rather than initial defects.

[0101] Step S203: Perform multiple consecutive temperature shock tests on the first test sample and the second test sample under the same conditions.

[0102] In this embodiment, the first test sample and the second test sample are placed in the same temperature test chamber and subjected to multiple consecutive temperature shock tests under exactly the same conditions.

[0103] A single temperature shock test includes a cooling phase, a low-temperature holding phase, a heating phase, and a high-temperature holding phase, performed sequentially.

[0104] In this embodiment, the initial temperature of the test samples is room temperature (approximately 25°C). Therefore, in the first temperature shock test, the temperature of the first and second test samples is reduced from room temperature to -40°C at a cooling rate of 80°C / h-100°C / h, with the first cooling phase lasting 1 to 1.5 hours. The low-temperature holding phase is maintained at -40°C for 1 to 2 hours. The heating phase is then carried out from -40°C to 105°C at a heating rate of 80°C / h-100°C / h, taking 1.5 to 2.5 hours. The high-temperature holding phase is maintained at 105°C for 1 to 2 hours. The first temperature shock test is thus completed.

[0105] Then, the temperature was lowered from 105℃ to -40℃ at a rate of 80℃ / h-100℃ / h, taking 1.5~2.5h; the low-temperature holding phase was maintained at -40℃ for 1h~2h; the heating phase was raised from -40℃ to 105℃ at a rate of 80℃ / h-100℃ / h, taking 1.5~2.5h; the high-temperature holding phase was maintained at 105℃ for 1h~2h. This completed the second temperature shock test.

[0106] Then, repeat the same temperature shock test as the second temperature shock test 3-6 times to complete the temperature shock test on the first and second test samples.

[0107] In this embodiment, the first and second test samples undergo 6-8 temperature shock tests to complete one test cycle. Each temperature shock test lasts 6-8 hours, and a complete test cycle takes 40-48 hours.

[0108] In this embodiment, different test samples are placed in the same test chamber at the same time to ensure that they undergo the exact same temperature shock process, which is the key to the reliability of the comparative test results.

[0109] Step S204: Perform electroluminescence detection on the first test sample to obtain a second electroluminescence image of the first test sample; perform electroluminescence detection on the second test sample to obtain a second electroluminescence image of the second test sample.

[0110] In this embodiment, after the first test sample and the second test sample have cooled to room temperature, electroluminescence detection is performed on the first test sample and the second test sample again to obtain the second electroluminescence image of the first test sample and the second electroluminescence image of the second test sample.

[0111] Step S205: Evaluate the temperature shock resistance of the solder joints of the battery cells in the first test sample and the temperature shock resistance of the solder joints of the battery cells in the second test sample, and compare the evaluation results of the first test sample and the second test sample.

[0112] In this embodiment, the temperature shock resistance of the cell weld joints in the first test sample and the second test sample are evaluated respectively, and the evaluation results of the two are compared.

[0113] According to the method of the aforementioned embodiment, the first electroluminescent image and the second electroluminescent image of the first test sample are compared, the color-changing areas are marked, the welding points of the color-changing areas are subjected to a tensile test to obtain the first pull-out force F11 of the welding points of the color-changing areas, and the welding points of the non-color-changing areas of the first test sample are subjected to a tensile test to obtain the second pull-out force F12 of the welding points of the non-color-changing areas. The first difference rate ΔF1 of the first pull-out force F11 and the second pull-out force F21 is calculated, and whether the welding points of the color-changing areas of the first test sample are abnormal is determined based on whether the first difference rate ΔF1 exceeds 30%.

[0114] In this embodiment, the same method is used to calculate the first pull-out force F21 and the second difference rate ΔF2 of the second pull-out force F21 of the second test sample. Whether the second difference rate ΔF2 exceeds 30% determines whether the welding point in the discolored area of ​​the second test sample is abnormal. The temperature shock resistance of the battery cell welding points in the first and second test samples is evaluated by comparing the first difference rate ΔF1 and the second difference rate ΔF2.

[0115] In this embodiment, different test samples are placed in the same test chamber for synchronous testing, ensuring that the temperature shock process experienced by different test samples is exactly the same. This eliminates errors such as environmental chamber differences and temperature fluctuations that may exist in different batches of tests. It can be used to evaluate the impact of variables such as cell type, welding parameters, and solder strips on test results, which is beneficial to the research and development and iteration of new materials and processes.

[0116] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps. It is understood that the steps in different embodiments can be freely combined as needed, and all non-contradictory solutions formed by such combinations are within the scope of protection of this application.

[0117] Based on the same inventive concept, this application also provides a photovoltaic cell performance testing device for implementing the photovoltaic cell performance testing method described above. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations in one or more photovoltaic cell performance testing device embodiments provided below can be found in the limitations of the photovoltaic cell performance testing method described above, and will not be repeated here.

[0118] In one exemplary embodiment, this application provides a performance testing apparatus for photovoltaic cells, referring to... Figure 6 The performance testing device for photovoltaic cells includes an electroluminescence detection module 301, a temperature testing module 302, and an evaluation module 303.

[0119] The electroluminescence detection module 301 is used to perform electroluminescence detection on the test sample to obtain a first electroluminescence image; the test sample includes at least two solar cells connected in series by solder strips.

[0120] The temperature testing module 302 is used to perform multiple consecutive temperature shock tests on the test sample; wherein, a single temperature shock test includes a cooling stage from a first temperature to a second temperature, a second temperature holding stage, a heating stage from the second temperature to the first temperature, and a first temperature holding stage.

[0121] The electroluminescence detection module 302 is also used to perform electroluminescence detection on the test sample after completing multiple temperature shock tests to obtain a second electroluminescence image;

[0122] Evaluation module 303 is used to evaluate the temperature shock resistance of the solder joints of the battery cells in the test sample based on the first electroluminescent image and the second electroluminescent image.

[0123] In one embodiment, the evaluation module 303 is used to compare the first electroluminescent image with the second electroluminescent image. If a local discolored area appears in the second electroluminescent image, the discolored area corresponds to the welding point. The first pull-out force of the discolored area is measured, and the second pull-out force of the welding point in the undiscolored area of ​​the test sample is measured. The difference rate between the first pull-out force and the second pull-out force is compared. If the difference rate between the first pull-out force and the second pull-out force exceeds a set threshold, it is determined that the welding point of the test sample has become abnormal after multiple temperature shock tests.

[0124] In one embodiment, during the temperature shock test, the first temperature is set between 100°C and 110°C, and the second temperature is set between -35°C and -45°C; and the total duration of multiple temperature shock tests is less than 48 hours.

[0125] In one embodiment, during the temperature shock test, the first temperature is 105°C and the second temperature is -40°C; the temperature change rate during the cooling phase is less than 100°C / hour; and the temperature change rate during the heating phase is less than 100°C / hour.

[0126] The temperature shock test is performed 4 to 20 times.

[0127] In one embodiment, when the electroluminescence detection module 301 performs electroluminescence detection on the test sample, it passes a forward test current in the same direction as the PN junction of the battery cell into the busbar of the battery cell. The magnitude of the forward test current is between 0.5 and 1.5 times the short-circuit current of the battery cell.

[0128] Each module in the aforementioned photovoltaic cell performance testing device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the computer device's memory as software, so that the processor can call and execute the corresponding operations of each module.

[0129] Thirdly, this application provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the above-described photovoltaic cell performance testing method.

[0130] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0131] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0132] 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 application.

[0133] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A performance testing method for photovoltaic cells, characterized in that, include: Prepare a test sample, the test sample comprising at least two battery cells connected in series by solder strips; Electroluminescence detection was performed on the test sample to obtain a first electroluminescence image; The test sample is subjected to multiple consecutive temperature shock tests; wherein a single temperature shock test includes a cooling phase from a first temperature to a second temperature, a second temperature holding phase, a heating phase from the second temperature to the first temperature, and a first temperature holding phase; wherein the temperature difference between the first temperature and the second temperature is greater than 130°C. After completing multiple temperature shock tests, electroluminescence detection was performed on the test sample to obtain a second electroluminescence image; Based on the first electroluminescent image and the second electroluminescent image, the temperature shock resistance of the welding points of the battery cells in the test sample is evaluated.

2. The performance testing method for photovoltaic cells according to claim 1, characterized in that, The evaluation of the temperature shock resistance of the solder joints of the battery cells in the test sample based on the first electroluminescent image and the second electroluminescent image includes: Comparing the first electroluminescent image with the second electroluminescent image, if a local discoloration area appears in the second electroluminescent image, the discoloration area corresponds to the welding point; Measure the first pull-out force of the discolored area and the second pull-out force of the weld point in the undiscolored area of ​​the test sample; Compare the difference rate between the first pull-out force and the second pull-out force. If the difference rate between the first pull-out force and the second pull-out force exceeds a set threshold, it is determined that the welding point of the test sample has become abnormal after multiple temperature shock tests.

3. The performance testing method for photovoltaic cells according to claim 1, characterized in that, In the temperature shock test, the first temperature is set between 100℃ and 110℃, and the second temperature is set between -35℃ and -45℃; and the total duration of multiple temperature shock tests is less than 48 hours.

4. The performance testing method for photovoltaic cells according to claim 3, characterized in that, In the temperature shock test, the first temperature is 105℃ and the second temperature is -40℃; the temperature change rate during the cooling phase is less than 100℃ / hour; and the temperature change rate during the heating phase is less than 100℃ / hour.

5. The performance testing method for photovoltaic cells according to claim 1, characterized in that, The temperature shock test is performed 4 to 20 times.

6. The performance testing method for photovoltaic cells according to claim 1, characterized in that, The test sample comprises 3-6 battery cells interconnected in series by solder strips, and busbars are welded to both ends of the test sample.

7. The performance testing method for photovoltaic cells according to claim 6, characterized in that, When performing electroluminescence detection on the test sample, a forward test current with the same direction as the PN junction of the battery cell is passed into the busbar of the battery cell. The magnitude of the forward test current is between 0.5 and 1.5 times the short-circuit current of the battery cell.

8. The performance testing method for photovoltaic cells according to claim 1, characterized in that, include: Prepare a first test sample and a second test sample, wherein the first test sample and the second test sample differ in at least one of the following: cell type or welding process; Electroluminescence detection was performed on the first test sample to obtain a first electroluminescence image of the first test sample. Electroluminescence detection was performed on the second test sample to obtain a first electroluminescence image of the second test sample; The first test sample and the second test sample were subjected to multiple consecutive temperature shock tests under the same conditions. Electroluminescence detection was performed on the first test sample to obtain a second electroluminescence image of the first test sample; Electroluminescence detection was performed on the second test sample to obtain a second electroluminescence image of the second test sample; The temperature shock resistance of the solder joints of the battery cells in the first test sample and the temperature shock resistance of the solder joints of the battery cells in the second test sample are evaluated, and the evaluation results of the first test sample and the second test sample are compared.

9. A performance testing device for photovoltaic cells, characterized in that, Includes an electroluminescence detection module, a temperature testing module, and an evaluation module: The electroluminescence detection module is used to perform electroluminescence detection on the test sample to obtain a first electroluminescence image; the test sample includes at least two battery cells connected in series by solder strips. The temperature testing module is used to perform multiple consecutive temperature shock tests on the test sample; wherein, a single temperature shock test includes a cooling phase from a first temperature to a second temperature, a second temperature holding phase, a heating phase from the second temperature to the first temperature, and a first temperature holding phase. The electroluminescence detection module is also used to perform electroluminescence detection on the test sample after completing multiple temperature shock tests to obtain a second electroluminescence image. The evaluation module is used to evaluate the temperature shock resistance of the welding points of the battery cells in the test sample based on the first electroluminescent image and the second electroluminescent image.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1-8.

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