Method for testing solar cell, testing system and storage medium

Abstract

The application discloses a kind of solar cell testing method and testing system and storage medium, method includes: obtaining the first PL brightness PL1 of the open circuit state of solar cell to be measured;Obtain the first color value M of the first surface and / or second surface of the solar cell to be measured;According to the PL1 and M of the solar cell to be measured, the target short-circuit current of the solar cell to be measured is calculated.This application, by adding the first color value of solar cell surface, that is, indirectly adding the optical information representing the surface of solar cell, combined with the electrical information of PL brightness, the short-circuit current density of the solar cell to be measured can be quickly and accurately obtained by non-contact method.In addition, during the grading process of solar cell, color camera is also needed, without additional color camera, without increasing the test cost.

Description

Technical Field

[0001] This application belongs to the field of photovoltaic technology, specifically relating to a test method, test system, and storage medium for solar cells. Background Technology

[0002] Accurately measuring the electrical properties of solar cells, such as short-circuit current density, is fundamental to evaluating their performance.

[0003] Currently, contact-based testing is commonly used to test the electrical performance of solar cells. This involves using test fixtures and conductive materials such as probes to test the electrical performance of solar cells.

[0004] However, in contact testing, good contact is mainly achieved by pressing probes and other test fixtures against the solar cell to perform performance testing. Firstly, the pressure applied to the solar cell by these tools has a certain probability of damaging the electrodes or even the passivation layer, causing microcracks or even cell breakage, reducing the yield and affecting the actual efficiency of the solar cell. Secondly, contact testing is also prone to poor probe contact or misalignment, leading to lower test stability, especially for back-contact solar cells. Using too many probes can also cause short circuits due to incorrect positive and negative electrode connections. Thirdly, the increasingly sophisticated printed patterns on solar cells and the shrinking effective contact windows pose significant challenges to the accuracy and stability of contact testing. Therefore, contact testing has certain limitations; furthermore, existing testing methods may also suffer from low accuracy. Summary of the Invention

[0005] This application aims to provide a testing method, testing system, and storage medium for solar cells, at least solving the aforementioned problems caused by contact testing and the problem of low testing accuracy.

[0006] In a first aspect, embodiments of this application propose a method for testing solar cells, comprising: The first PL brightness acquisition step involves acquiring the first PL brightness PL1 of the solar cell under test in the open-circuit state; in the thickness direction of the solar cell, the solar cell includes a first surface and a second surface opposite to each other; The first color value acquisition step involves acquiring the first color value M of the first surface and / or the second surface of the solar cell under test. The target short-circuit current density determination step involves calculating the target short-circuit current density of the solar cell under test based on PL1 and M.

[0007] In this application, firstly, the short-circuit current density test of solar cells can be performed in a non-contact manner at each step. The solar cell testing method of this application does not require the use of contact testing tools such as probes. Therefore, there is basically no risk of the electrodes and passivation layer of the solar cell being damaged by the probes. The risk of microcracks and cell cracks is low and will not affect the actual efficiency and yield of the solar cell. For back-contact solar cells, since probes are basically not used, the risk of short circuits caused by incorrect positive and negative electrode connections due to the use of overly dense probes is also avoided. Furthermore, the difficulty of accurately aligning the probes with the test points of the solar cell is also avoided. Therefore, the solar cell testing method provided in this application is applicable to various types of solar cells and has a wide range of applications, even for back-contact solar cells without a main grid.

[0008] Secondly, the color change of a solar cell is the result of the combined effects of its surface morphology and film thickness, and is closely related to surface reflection escape loss and parasitic absorption of the film. More specifically, the first color value here is closely related to the optical constants of the solar cell, which mainly refer to film thickness, refractive index, extinction coefficient, etc. The optical constants determine the absorptivity, which can characterize absorption loss. Usually, PL brightness can reflect the electrical performance of a solar cell. However, the short-circuit current density characterized by PL brightness does not take absorption loss into account. Therefore, in this application, by adding the first color value of the solar cell surface, optical information or absorption loss representing the solar cell surface is indirectly added. Combined with the electrical information of PL brightness, the short-circuit current density of the solar cell under test can be obtained quickly and more accurately through a non-contact method.

[0009] Third, color cameras are also needed in the process of classifying solar cells, so no additional color camera is needed to obtain the first color value in this application. Color cameras from other processes can be reused directly, without increasing the testing cost.

[0010] In summary, this application improves the accuracy of non-contact testing while keeping testing costs in mind and does not increase testing costs.

[0011] In some embodiments, the target short-circuit current density determination step includes: Substitute the PL1 and M of the solar cell under test into the preset relationship of short-circuit current density corresponding to the cell type of the solar cell under test, and calculate the target short-circuit current density Jsc of the solar cell under test. The preset relationship for the short-circuit current density is: Jsc = (PL1 - E × M) × F + G; E, F and G are all constants.

[0012] In some embodiments, prior to the target short-circuit current density determination step, the method further includes: a short-circuit current density preset relationship determination step. For multiple solar cells of the cell type of the solar cell under test: The contact short-circuit current density of each solar cell was obtained using a contact-type test method. Obtain the second PL brightness PL2 of each solar cell in the open-circuit state; Obtain the second color value of the first and / or second surface of each solar cell; Based on multiple contact-type short-circuit current densities, multiple second PL brightness values, and multiple second color values, a preset relationship for the short-circuit current density corresponding to the cell type of the solar cell under test is obtained by fitting, as well as E, F, and G in the preset relationship for the short-circuit current density corresponding to the cell type of the solar cell under test.

[0013] In some embodiments, the first color value acquisition step includes: Obtain the RGB values ​​of the first and / or second surfaces of the solar cell under test, convert the RGB values ​​to HSV or Lab values, and then... Convert the HSV value to the first color value, where A1, B1, and D1 are all constants greater than or equal to 0, and A1 > D1 ≥ B1; or, according to The Lab value is converted into the first color value, where A2, B2, and D2 are all constants greater than or equal to 0, and D2≥B2>A2.

[0014] In some embodiments, the first PL brightness acquisition step includes: acquiring the PL11 of the solar cell under test in an open-circuit state when it is illuminated by a first preset illumination; the first preset illumination is 0.01 to 0.2 standard solar irradiance. The method further includes: The EL1 acquisition step involves acquiring the electroluminescence value EL1 of the solar cell under test when it is exposed to the first preset light in an open-circuit state. The equivalent voltage drop acquisition step involves determining the first equivalent voltage drop of the solar cell under test based on PL11 and EL1. ; The target series resistance determination step involves determining the first equivalent voltage drop of the solar cell under test. Substitute the preset relationship of series resistance corresponding to the cell type of the solar cell under test into the formula to calculate the target series resistance Rs of the solar cell under test. The preset formula for the series resistance is: Rs = X × +Q; X and Q are both constants.

[0015] In some embodiments, prior to the target series resistance determination step, the method further includes a series resistance preset relationship determination step; For multiple solar cells of the cell type of the solar cell under test: The contact series resistance of each solar cell was obtained using a contact-type testing method. Obtain PL3 under the first preset illumination when each solar cell is in an open-circuit state; Obtain the electroluminescence value EL2 of each solar cell under the first preset illumination when it is in the open-circuit state; The second equivalent voltage drop of each solar cell is determined based on PL3 and the electroluminescence value EL2; Based on multiple contact short-circuit current densities and multiple second equivalent voltage drops, a preset relationship for the series resistance corresponding to the cell type of the solar cell under test is obtained by fitting, as well as X and Q in the preset relationship for the series resistance corresponding to the cell type of the solar cell under test.

[0016] In some embodiments, before the first PL brightness acquisition step, the method further includes: dividing the solar cell under test into multiple regions; The first PL brightness acquisition step includes: for each region, acquiring the PL11 of the region under the first preset illumination when the solar cell under test is in an open-circuit state; The EL1 acquisition step includes: for each region, acquiring the electroluminescence value EL1 of the region under the first preset illumination when the solar cell under test is in an open-circuit state; The equivalent voltage drop acquisition step includes: for each region, determining the first equivalent voltage drop of the solar cell under test based on the PL11 and EL1 corresponding to the region. ; Calculate the first equivalent voltage drop across all regions of the solar cell under test. The average value.

[0017] In some embodiments, the first PL brightness acquisition step includes: for at least three second preset light intensities: acquiring PL12 when the solar cell under test is irradiated by each second preset light in the open-circuit state; The method further includes: The equivalent current density determination step involves determining the equivalent current density corresponding to each second preset illumination based on the short-circuit current density of the solar cell under test. The first voltage determination step involves determining the equivalent voltage under each second preset light intensity irradiation based on PL12. The IV curve determination step involves plotting a portion of the IV curve of the solar cell under test based on the equivalent current density and equivalent voltage corresponding to the at least three second preset light intensities. The first conversion efficiency determination step involves determining the maximum quasi-conversion efficiency of the solar cell under test based on a portion of its IV curve. The target conversion efficiency determination step involves determining the target conversion efficiency of the solar cell under test based on its series resistance and maximum quasi-conversion efficiency.

[0018] In some embodiments, the short-circuit current density of the solar cell under test is the target short-circuit current density of the solar cell under test; and / or, The series resistance of the solar cell under test is the target series resistance Rs of the solar cell under test; and / or, The solar cell under test is a crystalline silicon solar cell, and the second preset light intensity includes at least 0.03 to 0.07 standard solar intensities.

[0019] In some embodiments, the target conversion efficiency determination step includes: Substitute the series resistance R1 and the maximum quasi-conversion efficiency pEta of the solar cell under test into the preset conversion efficiency relationship corresponding to the cell type of the solar cell under test, and calculate the target conversion efficiency Eta of the solar cell under test. The preset formula for the conversion efficiency corresponding to the cell type of the solar cell under test is: Eta = (pEta - Y × R1) × T + Z, where Y, T and Z are all constants.

[0020] In some embodiments, prior to the target conversion efficiency determination step, the method further includes: For at least three second preset light intensities, the cell type of the solar cell under test includes multiple solar cells: The contact conversion efficiency of each solar cell was obtained using a contact testing method. Obtain PL4 for each second preset illumination under the open-circuit state of each solar cell; Based on the short-circuit current density of each solar cell, determine the equivalent current density corresponding to each second preset illumination. For each solar cell, the equivalent voltage under each second preset light intensity irradiation is determined according to PL4; For each solar cell, a partial IV curve of the solar cell is plotted based on the equivalent current density and equivalent voltage corresponding to at least three second preset light intensities. For each solar cell, the maximum quasi-conversion efficiency of the solar cell is determined based on a portion of its IV curve. Based on the series resistance and maximum quasi-conversion efficiency of multiple solar cells, a preset conversion efficiency formula corresponding to the cell type of the solar cell under test is obtained by fitting, as well as Y, T, and Z in the preset conversion efficiency formula corresponding to the cell type of the solar cell under test.

[0021] In some embodiments, the PL brightness acquisition step includes: acquiring the PL brightness at least at the edge positions of the solar cell, and / or acquiring the PL brightness at least at the corner positions of the solar cell; and / or, In the color value acquisition step: acquire the color value at least at the edge position of the first surface of the solar cell, and / or acquire the color value at least at the corner position of the first surface of the solar cell; and / or acquire the color value at least at the edge position of the second surface of the solar cell, and / or acquire the color value at least at the corner position of the second surface of the solar cell.

[0022] In some embodiments, the PL brightness acquisition step involves acquiring the PL brightness of the solar cell under illumination of 0.01 to 0.2 standard solar intensities.

[0023] In some embodiments, prior to acquiring the PL brightness, the method further includes: Acquire a color image containing the background where the solar cell is located, and at least the edge regions of the first and / or second surfaces of the solar cell; Acquire a background containing the solar cell and a light-emitting image of the solar cell in an open-circuit state, the light-emitting image including a sub-light-emitting image of the solar cell in the open-circuit state; Based on the color image, the portion of the battery edge region in the luminescent image that was mistakenly identified as the background of the solar cell is added to the sub-luminescent image to obtain the luminescent image of the solar cell in the open-circuit state; The PL brightness acquisition includes: acquiring the PL brightness of the solar cell in the open-circuit state based on the emission image of the solar cell.

[0024] Secondly, embodiments of this application propose a testing system for solar cells, comprising: A photoluminescence tester is used to obtain the first PL brightness PL1 of the solar cell under test; in the thickness direction of the solar cell, the solar cell includes a first surface and a second surface opposite to each other; An optical inspection instrument is used to acquire the first color value M of the first surface and / or the second surface of the solar cell under test; The target short-circuit current density determination module is used to calculate the target short-circuit current of the solar cell under test based on PL1 and M.

[0025] Thirdly, embodiments of this application propose a computer-readable storage medium storing a computer program / instructions thereon, which, when executed by a processor, implements any of the aforementioned solar cell testing methods.

[0026] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0027] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a flowchart of the testing steps for a solar cell according to an embodiment of this application; Figure 2 This is a schematic diagram of a light source illuminating a solar cell under test according to an embodiment of this application.

[0028] Figure label: 2-Solar cell under test, 21-Collector electrode, 6-Emission image, 61-Local photoluminescence image, 62-Local electroluminescence image. Detailed Implementation

[0029] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting 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.

[0030] This application provides a testing method for solar cells, referring to... Figure 1 The testing method may specifically include the following steps.

[0031] Step S1, First PL Brightness Acquisition Step, acquire the first PL brightness PL1 of the solar cell under test in the open circuit state; in the thickness direction of the solar cell, the solar cell includes a first surface and a second surface opposite to each other.

[0032] A light source can be used to illuminate the open-circuit solar cell under test with light energy of varying intensity. The solar cell under test is excited and produces photoluminescence or fluorescence in a specific wavelength band corresponding to the excitation intensity. A light-harvesting device, such as a camera, captures the photoluminescence or fluorescence and generates a corresponding emission image. This emission image can be a photoluminescence image. Then, based on the aforementioned photoluminescence image, the first PL brightness (photoluminescence intensity value) PL1 of the open-circuit state of the solar cell under test is obtained. The specific acquisition of PL1 is not limited.

[0033] For example, after obtaining the emission image of the solar cell under test in the open circuit state under a certain light intensity, the average value of the photoluminescence intensity of all pixels in the emission image is calculated based on the photoluminescence intensity value of each pixel in the emission image, and the average value is used as PL1 of the solar cell under test in the open circuit state under that light intensity.

[0034] In some embodiments, obtaining the PL1 in this application may include: dividing the solar cell under test into multiple regions (multiple regions refer to more than two regions), then acquiring a photoluminescence image of the solar cell under test in an open-circuit state under a certain light intensity, calculating the average of the photoluminescence intensity values ​​of all regions in the photoluminescence image based on the photoluminescence intensity value of each region in the photoluminescence image, and using this average value as the PL1 of the solar cell under test in an open-circuit state under that light intensity. Compared to the numerous pixels in the photoluminescence image, this application divides the solar cell under test into regions, resulting in a relatively small number of regions, thus significantly reducing the computational load and improving testing efficiency.

[0035] It should be noted that during the region division process, the solar cell can be divided into multiple regions evenly, or more regions can be divided for areas of the solar cell that are sensitive to PL brightness or have weak passivation and many defects, while fewer regions can be divided for areas with good passivation and fewer defects. For example, the edges and corners of solar cells often have passivation defects, so more regions can be divided for these areas to further improve the accuracy of the obtained PL brightness.

[0036] In some embodiments, in this application, all steps for obtaining the PL brightness can involve obtaining the PL brightness of the solar cell under low light intensity, such as 0.01 to 0.2 standard solar irradiances. Specifically, firstly, current solar cells commonly use high-resistivity substrates. Under high light intensity, such as 1 or close to 1 standard solar irradiance, many photogenerated carriers are generated, resulting in insufficient exposure of defects in the emission image. However, under low light intensity, such as 0.01 to 0.2 standard solar irradiances, the defects of the solar cell are more clearly displayed in the PL brightness. Therefore, obtaining the PL brightness under low light intensity, such as 0.01 to 0.2 standard solar irradiances, can more fully expose the defects of the solar cell, allowing the defects of the solar cell to be more clearly revealed. In the current testing results of solar cells, two methods can be used to improve the accuracy of solar cell testing. Secondly, for common crystalline silicon solar cells, the light intensity corresponding to their maximum efficiency or maximum power point resistance value is usually located in the range of low light intensity, such as 0.01 to 0.2 standard solar irradiance. Therefore, obtaining the PL brightness under low light intensity, such as 0.01 to 0.2 standard solar irradiance, allows the relevant information of the maximum efficiency or maximum power point of the solar cell to be reflected in the solar cell test results, which can also improve the accuracy of solar cell testing.

[0037] For example, the PL brightness of the solar cell in open-circuit state under low light intensity, such as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.09, 0.1, 0.13, 0.15, 0.18, and 0.2 standard solar irradiances, can be obtained respectively.

[0038] In this application, the specific form of different light intensities is not limited. For example, the initial light intensity, the final light intensity, and the total number of light intensities or increments to be added each time can be set. Then, starting from the initial light intensity, the light intensity is increased sequentially according to the corresponding increase method each time. The light intensity increases each time can be equal or unequal. The solar cell under test is illuminated, and the emission image of the solar cell under test is acquired under each illumination until the final light intensity is reached. The specific number of light intensity increments from the initial light intensity to the final light intensity is not limited. For example, the light intensity from the initial light intensity (greater than 0) to the final light intensity can be divided into approximately 3 to 20 light intensity increments. The total number of light intensity increments can be set as follows: more light intensity increments can be set near the light intensity corresponding to the potentially higher power of the solar cell under test, and more light intensity increments can also be set in the low light intensity range, thereby enhancing the accuracy of the test parameters such as maximum power. For the same solar cell under test, approximately 3 to 20 emission images can be obtained.

[0039] In the thickness direction of the solar cell, the solar cell includes a first surface and a second surface opposite to each other. One of the first surface and the second surface is the light-facing surface and the other is the back-lighting surface. During normal operation of the solar cell, the surface that mainly receives light is the light-facing surface, and the back-lighting surface is opposite to the light-facing surface.

[0040] In some embodiments, before acquiring each PL brightness, the testing method may further include: acquiring a color image containing the background where the solar cell is located, and at least the edge region of the first surface and / or the second surface of the solar cell; acquiring a light emission image containing the background where the solar cell is located, and the solar cell in an open-circuit state, the light emission image including a sub-light emission image of the solar cell in the open-circuit state; based on the aforementioned color image, filling in the sub-light emission image with the portion of the cell edge region in the light emission image that is mistakenly calculated as the background where the solar cell is located, to obtain a light emission image of the solar cell in the open-circuit state; acquiring the PL brightness includes: acquiring the PL brightness of the solar cell in the open-circuit state based on the light emission image of the solar cell. Specifically, during the acquisition of the emission image of a solar cell in its open-circuit state, defects such as over-plating and over-etching are prone to occur at least in the edge areas of the first and / or second surfaces of the solar cell. Therefore, the PL (Power Radiation) brightness of these areas is relatively low, especially under low light conditions. Since the background of the solar cell is also very dark in the emission image, the edge areas of the first and / or second surfaces cannot be effectively distinguished from the background. This leads to the solar cell edge being mistaken for the background, meaning the sub-emission image of the open-circuit solar cell may not include the edge area. Consequently, the non-contact measurement of solar cell efficiency and other test parameters may be slightly higher than the actual parameters, resulting in inaccuracy. Therefore, this application addresses this issue by adding a reference color image of the first and / or second surfaces at least in their edge areas. This allows for the accurate determination of the solar cell's boundary lines or contours in the emission image, thus filling in the incorrectly identified edge areas of the solar cell in the emission image. This improves the accuracy of the measurement of solar cell efficiency and other test parameters.

[0041] Specifically, color images can be used to accurately determine the size of solar cells and certain specific locations within them. Then, by using the size and specific locations of solar cells, the area where the solar cells are located can be accurately selected from the luminous image containing the background. This allows for the accurate identification or differentiation of the background and the edges of the solar cells from the luminous image containing the background.

[0042] It should be noted that, due to manufacturing errors during the processing of the same type of solar cell substrate, its dimensions may fluctuate to some extent, for example, by approximately ±1.5mm. Therefore, this application, through additional color image calibration, can avoid the impact of manufacturing errors on cell dimensions, further improving the accuracy of non-contact testing of solar cells. Furthermore, color cameras are also required in processes such as solar cell grading; therefore, this application does not require an additional color camera for acquiring color images, as color cameras from other processes can be reused without increasing testing costs. Thus, this application further improves testing accuracy without increasing testing costs.

[0043] Each PL brightness measurement may utilize a color image to distinguish between the background and the edge of the solar cell, and the portion of the cell edge area in the aforementioned emission image that is mistakenly identified as the background of the solar cell may be added to the sub-emission image. Alternatively, some PL brightness measurements may utilize a color image to distinguish between the background and the edge of the solar cell, and the portion of the cell edge area in the aforementioned emission image that is mistakenly identified as the background of the solar cell may be added to the sub-emission image, while other PL brightness measurements may not utilize a color image to distinguish between the background and the edge of the solar cell. All of these methods fall within the scope of protection of this application. For example, during the measurement of PL1 of the solar cell under test, a color image can be used to distinguish between the background and the edge of the solar cell, and the portion of the cell edge area in the aforementioned emission image that is mistakenly identified as the background of the solar cell may be added to the sub-emission image, thereby significantly improving the accuracy of test parameters such as short-circuit current.

[0044] Step S2, First color value acquisition step, acquire the first color value M of the first surface and / or the second surface of the solar cell under test.

[0045] A color camera or similar device can be used to obtain the first color value M of the first and / or second surfaces of the solar cell under test. Since color cameras are also required in processes such as solar cell grading, this application eliminates the need for an additional color camera to obtain the first color value; color cameras used in other processes can be reused without increasing testing costs.

[0046] The aforementioned PL brightness reflects the electrical performance of the solar cell under test. The first color value M of this application reflects the color change of the solar cell under test, or in other words, the first color value M reflects the combined effect of the surface morphology, film thickness, and optical parameters (such as refractive index and extinction coefficient) of the solar cell under test. It is closely related to the surface reflection escape loss and parasitic absorption of the film layer. The color change, or optical aspect, of the solar cell surface is actually the main point of difference in the short-circuit current change of the solar cell. Therefore, by adding the first color value of the solar cell surface in this application, optical information representing the solar cell surface is indirectly added. Combined with the electrical information of PL brightness, the short-circuit current density of the solar cell under test can be obtained quickly and more accurately through a non-contact method.

[0047] It can be that only the first color value M of the first surface of the solar cell under test is obtained, or only the first color value M of the second surface is obtained, or both the first color value M of the first surface and the first color value M of the second surface of the solar cell under test are obtained.

[0048] In some embodiments, step S2 may include: obtaining a first color value M of the light-facing surface of the solar cell under test. Specifically, the light received by a solar cell mainly comes from its light-facing surface, while less light is obtained from its back surface. Therefore, the color change of its light-facing surface is more closely related to the surface reflection escape loss and film parasitic absorption of the solar cell under test. Therefore, in this application, by increasing the first color value M of the light-facing surface of the solar cell under test, the front reflection escape loss and film parasitic absorption of the solar cell under test are reflected in the test results, thereby further improving the accuracy of the test.

[0049] In some embodiments, the step of obtaining the first color value M here may include: obtaining the RGB (R corresponds to red, G corresponds to green, B corresponds to blue) values ​​of the first and / or second surfaces of the solar cell under test, converting the RGB values ​​into HSV (H refers to hue, S refers to saturation, V refers to intensity) values ​​or Lab (L refers to intensity, a refers to red-green color components, b refers to yellow-blue color components) values, and according to... Convert the HSV value to the first color value. In this formula, H is the hue (H) of the RGB value converted to HSV, S is the saturation (S) of the RGB value converted to HSV, and V is the lightness (V) of the RGB value converted to HSV. A1, B1, and D1 are all constants greater than or equal to 0, and A1 > D1 ≥ B1. Or according to The Lab value is converted to the first color value. In this formula, L is the lightness (L) of the RGB value converted to Lab, a is the red-green chromaticity component (a) of the RGB value converted to Lab, and b is the yellow-blue chromaticity component (b) of the RGB value converted to Lab. A², B², and D² are all constants greater than or equal to 0, and D² ≥ B² > A². Specifically, RGB is more hardware-oriented, and RGB data can be obtained using common color cameras, resulting in relatively low hardware costs. HSV and Lab are more compatible with the human eye, making them easier for the human eye to distinguish, and they are also more resistant to interference from changes in lighting. By converting RGB to HSV or Lab and then to the desired first color value M, interference from changes in lighting can be resisted, improving the stability of the test, while requiring lower hardware costs.

[0050] It should be noted that the conversion from RGB to HSV can be performed using existing conversion methods, and the conversion from RGB to Lab can be performed using existing matrix multiplication and other methods. This application does not limit the scope of the conversion.

[0051] In some embodiments, a camera capable of directly outputting HSV and Lab values ​​can be used to acquire the HSV and Lab values ​​of the first and / or second surfaces of the solar cell under test. Alternatively, a camera capable of outputting RGB values ​​can be used to acquire the RGB values ​​of the first and / or second surfaces of the solar cell under test, and then the values ​​can be converted to HSV and Lab values ​​using existing conversion methods. Compared to cameras that directly output HSV and Lab values, cameras that output RGB values ​​are relatively cheaper, and the conversion from RGB to HSV and from RGB to Lab values ​​is currently mature and inexpensive, which can reduce costs.

[0052] In some embodiments, during the process of calculating and obtaining the first color value M, In this context, A1, B1, and D1 are all constants greater than or equal to 0, and A1 > D1 ≥ B1. For example, A1 is 1.2, D1 is 1, and B1 is 0.8; or, B1 and D1 are both 0, A1 > 0, or A1 > D1 > 0, and B1 is 0. Specifically, as mentioned above, the light-facing side or front side of a solar cell is its main light-absorbing side. Therefore, the first color value of the light-facing side of the solar cell has a greater impact on the test accuracy of the solar cell. Typically, due to the presence of structures such as the passivation and antireflection layer on the front side, such as a silicon nitride film, a large area of ​​the light-facing side of the solar cell appears blue or close to blue. In the HSV color space, the first color value of the light-facing side of the solar cell is not sensitive enough to the lightness corresponding to V and the saturation corresponding to S, but is more sensitive to the hue corresponding to H. Therefore, in this application, by selectively setting the values ​​of A1, B1, and D1, not only can the amount of calculation be reduced and the detection efficiency improved, but the test accuracy can also be improved.

[0053] It should be noted that for A1>D1≥B1, A1, D1, and B1 are all constants greater than or equal to 0 as mentioned above, and A1>D1≥B1 is sufficient.

[0054] In some embodiments, during the process of calculating and obtaining the first color value M, In this context, A2, B2, and D2 are all constants greater than or equal to 0, and D2 ≥ B2 > A2. For example, if A2 is 0, then D2 ≥ B2 > 0. Specifically, as mentioned earlier, the light-facing side or front side of a solar cell is its main light-absorbing side. Therefore, the first color value of the light-facing side of the solar cell has a greater impact on the test accuracy of the solar cell. Typically, due to the presence of structures such as the passivation antireflection layer on the front side, the light-facing side of the solar cell appears blue or close to blue over a large area. In the Lab color space, the first color value of the light-facing side of the solar cell is not sensitive enough to the lightness corresponding to L and the red-green chromaticity component corresponding to a, but is more sensitive to the yellow-blue chromaticity component corresponding to b. Therefore, in this application, by selectively setting the values ​​of A2, B2, and D2, not only can the amount of calculation be reduced and the detection efficiency improved, but the test accuracy can also be improved.

[0055] It should be noted that for D2≥B2>A2, A2, D2, and B2 are all constants greater than or equal to 0, and D2≥B2>A2 is sufficient.

[0056] The execution order of steps S1 and S2 is not limited here. For example, S1 can be executed first, followed by S2, or S2 can be executed first, followed by S1.

[0057] Step S3, the target short-circuit current density determination step, calculates the target short-circuit current density of the solar cell under test based on PL1 and M of the solar cell under test.

[0058] As mentioned earlier, PL1 can reflect the electrical information of the solar cell under test, while M can reflect the optical information of the solar cell under test. Based on this, the target short-circuit current density of the solar cell under test can be accurately obtained.

[0059] Therefore, in this application, the short-circuit current density test of solar cells can be performed using non-contact methods. The solar cell testing method of this application eliminates the need for contact testing tools such as probes, thus minimizing the risk of probe damage to the electrodes and passivation layer of the solar cell. The risk of microcracks and wafer breakage is low, and it will not affect the actual efficiency and yield of the solar cell. For back-contact solar cells, since probes are largely not used, the risk of short circuits caused by misalignment of positive and negative electrodes due to excessively dense probes is avoided, as is the difficulty of precisely aligning the probe with the test points of the solar cell. Therefore, the solar cell testing method provided in this application is applicable to various types of solar cells, with a wide range of applications, even for back-contact solar cells without a main grid. Furthermore, the color change of a solar cell is the result of the combined effects of the solar cell surface morphology and film thickness, and it is highly correlated with surface reflection escape loss and parasitic absorption of the film layer. More specifically, the first color value here is closely related to the optical constants of the solar cell. Optical constants mainly refer to film thickness, refractive index, extinction coefficient, etc. These optical constants determine the absorptivity, which characterizes absorption loss. Typically, PL (plastic area) brightness reflects the electrical performance of the solar cell. However, the short-circuit current density represented by PL brightness does not consider absorption loss. Therefore, in this application, by adding the first color value of the solar cell surface, optical information or absorption loss representing the solar cell surface is indirectly added. Combined with the electrical information of PL brightness, the short-circuit current density of the solar cell under test can be obtained quickly and more accurately through a non-contact method. Furthermore, color cameras are also needed in processes such as classifying solar cells. Therefore, obtaining the first color value in this application does not require an additional color camera; color cameras from other processes can be reused without increasing testing costs. In summary, this application improves the accuracy of non-contact testing while also considering testing costs, without adding any additional testing fees.

[0060] It should be noted that in this application, when determining the target short-circuit current density of the solar cell under test using the first PL brightness PL1, at least one irradiance can be selected within the range of 0.01 to 0.2 standard solar irradiance to obtain the target short-circuit current density of the solar cell under test.

[0061] In some embodiments, the PL brightness acquisition step of this application involves: acquiring the PL brightness at least at the edge positions of the solar cell, and / or acquiring the PL brightness at least at the corner positions of the solar cell. The color value acquisition step of this application involves: acquiring the color value at least at the edge positions of the first surface of the solar cell, and / or acquiring the color value at least at the corner positions of the first surface of the solar cell; and / or acquiring the color value at least at the edge positions of the second surface of the solar cell, and / or acquiring the color value at least at the corner positions of the second surface of the solar cell. Then, using the PL brightness at the edge positions and corner positions, and the color values ​​at the edge positions and corner positions, the performance parameters such as the short-circuit current density of the solar cell under test can be determined. Specifically, the edge and corner positions of solar cells, due to their outer location or abrupt shape changes, are prone to defects such as over-plating, over-etching, and incomplete film coverage. These are locations where defects are more likely to occur in solar cells. In this application, by increasing the PL and color values ​​at these locations, the defect information of the solar cell can be accurately reflected in the detection results, further improving the detection accuracy.

[0062] It should be noted that the edge position of a solar cell refers to the location close to and within the edge line of the solar cell. The corner position of a solar cell refers to the location at or near the corner of the solar cell.

[0063] It is possible for each PL brightness measurement to acquire the PL brightness at the edge and corner positions of the solar cell, or for some PL brightness measurements to acquire the PL brightness at the edge and corner positions of the solar cell, while others do not, all of which are within the scope of protection of this application. For example, during the measurement of PL1 of the solar cell under test, the PL brightness at the edge and corner positions of the solar cell can be acquired, thereby significantly improving the accuracy of test parameters such as short-circuit current.

[0064] In some embodiments, step S3 may include: substituting the aforementioned PL1 and M of the solar cell under test into the preset short-circuit current density formula corresponding to the cell type of the solar cell under test, to calculate the target short-circuit current density Jsc of the solar cell under test; where Jsc = (PL1 - E × M) × F + G; E, F, and G are all constants. This preset short-circuit current density formula is obtained through contact measurement calibration. In actual use, when measuring the short-circuit current density of the solar cell under test, contact measurement is no longer required; only the aforementioned PL1 and M are needed, which is not only highly accurate but also quick and convenient. E, F, and G are specifically related to the cell type; different cell types may correspond to different values ​​for E, F, and G. It should be noted that, as mentioned earlier, PL brightness typically reflects the electrical performance of the solar cell. The short-circuit current density characterized by PL brightness does not consider absorption loss, while the first color value M reflects absorption loss. Therefore, subtracting the two values ​​accurately characterizes the actual short-circuit current density of the solar cell under test.

[0065] In some embodiments, before using the preset short-circuit current density formula, the method may further include: a step of establishing the preset short-circuit current density formula, specifically: for multiple solar cells of the cell type of the solar cell under test: using a contact test method to obtain the contact short-circuit current density of each solar cell; obtaining the second PL brightness PL2 of each solar cell in the open-circuit state; obtaining the second color value of the first surface and / or the second surface of each solar cell; and fitting the preset short-circuit current density formula corresponding to the cell type of the solar cell under test, as well as E, F, and G in the preset short-circuit current density formula corresponding to the cell type of the solar cell under test, based on the multiple contact short-circuit current densities, the multiple second PL brightness, and the multiple second color values. The fitting method can be a linear fitting method, etc., and the multiple parameters here can be hundreds or even thousands. By fitting the above-mentioned multiple parameters of the same cell type to obtain the above-mentioned formula, it has universality for solar cells of that cell type, thereby determining the short-circuit current density of the solar cell under test of that type with high accuracy.

[0066] It should be noted that in the process of establishing the preset relationship of short-circuit current density corresponding to the cell type of the solar cell under test, the acquisition methods of the second PL brightness and the second color value are the same as those of the first PL brightness and the first color value, as well as the background, and will not be repeated here.

[0067] In some embodiments, the test method further includes a test step for the series resistance of the solar cell under test. The aforementioned step S1 may include step S101, and the test method may further include the following steps S4 to S6.

[0068] Step S101: Obtain PL11 when the solar cell under test is in an open-circuit state and is illuminated by a first preset illumination; the first preset illumination is 0.01 to 0.2 standard solar intensity.

[0069] Similar to the aforementioned description, current solar cells commonly use high-resistivity substrates. Under high light intensity, such as 1 or close to 1 standard solar irradiance, a large number of photogenerated carriers are generated, resulting in insufficient exposure of defects in the emission image. However, under low light intensity, such as 0.01 to 0.2 standard solar irradiance, the defects of solar cells are more clearly displayed in the photoluminescence (PL) brightness. Therefore, obtaining the PL brightness under low light intensity, such as 0.01 to 0.2 standard solar irradiance, can more fully expose the defects of solar cells, allowing these defects to be reflected in the light emission image. The test results of the series resistance of solar cells can improve the accuracy of solar cell testing. In addition, for common crystalline silicon solar cells, the light intensity corresponding to their maximum efficiency or maximum power point resistance value is usually located in the range of low light intensity, such as 0.01 to 0.2 standard solar irradiance. Therefore, obtaining the PL brightness under low light intensity, such as 0.01 to 0.2 standard solar irradiance, allows the relevant information of the maximum efficiency or maximum power point of the solar cell to be reflected in the resistance test results of the solar cell, which can also improve the accuracy of solar cell testing.

[0070] For example, the open-circuit state of the solar cell can be obtained under low light intensity, such as under standard solar intensity of 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.09, 0.1, 0.13, 0.15, 0.18, and 0.2 standard solar intensities.

[0071] PL11 can be obtained as the PL intensity when the entire surface of the solar cell under test is within the range of 0.01 to 0.2 standard solar irradiance, or the PL intensity when the entire surface of the solar cell under test is illuminated by light within the range of 0.01 to 0.2 standard solar irradiance. Alternatively, refer to... Figure 2The surface of the solar cell under test 2, which is in relative motion, is illuminated by a light source to form an illumination area of ​​width W (corresponding to the area indicated by the local photoluminescence image 61). The local photoluminescence image 61 of the illumination area and the local electroluminescence images 62 excited by the induced current on both sides of the illumination area in the direction of motion are acquired. Both the photoluminescence image and the electroluminescence image are emission images 6. The aforementioned PL11 acquisition step includes stitching the aforementioned local photoluminescence images 61 to obtain a full-surface photoluminescence image of the solar cell under test in the open-circuit state, and acquiring the PL11 from the full-surface photoluminescence image of the solar cell under test in the open-circuit state. The light source forming the illumination area can be a line-scanned laser source. The orthographic projection of the line-scanned laser source on the solar cell under test 2 is a strip or line shape, so the area illuminated on the solar cell under test 2 is a strip or line area. The orthographic projection length of the line-scanned laser source is basically consistent with the size of the solar cell under test in the X direction, so that the illumination area can cover the entire effective power generation area of ​​the solar cell under test in the X direction, improving detection efficiency and accuracy. When a line-scanned laser light source is used, the laser wavelength can range from 750nm to 1400nm, for example, wavelengths such as 840nm and 950nm, and the power can be greater than 5W / cm². 2 The appropriate light source can be selected as long as it matches the spectral response of the solar cell under test and ensures sufficient laser excitation to generate photogenerated carriers and induced current, and is not limited to the wavelengths and powers listed in this embodiment. Alternatively, the light source forming the illumination area can be an array light source. A mask is placed at the exit port of the array light source or above the solar cell under test. The orthographic projection length of the actual illumination light source obtained by the array light source through the mask on the solar cell under test is the size of the solar cell under test in the X direction. Both the X direction and the length direction of the orthographic projection of the solar cell under test are perpendicular to the Y direction. The array light source can be an LED lamp containing several LED beads to form an array light source. The array light source emits non-parallel diffused light. In order to form a strip-shaped illumination area on the solar cell under test, a mask is placed at the exit port of the array light source or above the solar cell under test. The actual illumination light source obtained by the light source through the mask is a strip-shaped area. The orthographic projection length of the actual illumination light source on the solar cell under test is basically consistent with the size of the solar cell under test in the X direction, so that the illumination area can cover the entire effective power generation area of ​​the solar cell under test in the X direction, improving detection efficiency and accuracy. Since the orthographic projection width W of the actual irradiated light source on the solar cell under test 2 depends on the pattern width on the mask, and the cost of the array light source is lower than that of the line-scan laser light source, the orthographic projection width of the actual irradiated light source after the array light source passes through the mask is not limited. The array light source may need to irradiate the solar cell under test at least twice to collect a complete light energy image of the solar cell under test.

[0072] In some embodiments, refer to Figure 2 The solar cell under test 2 includes a current collector 21, and the direction Y of the width W of the irradiated area intersects with the extension direction X of the current collector 21. Specifically, the current collector 21 is used to collect the current or charge carriers in the solar cell under test 2. The local electroluminescent image 62 is excited by the induced current. The direction of the width W intersects with the extension direction X of the current collector 21. The transmission distance of the induced current is smaller, and the current conduction can be faster, improving the image quality of the local electroluminescent image 62 and further improving the detection accuracy of EL1. The angle between the direction Y of the width W of the irradiated area and the extension direction X of the current collector 21 is not limited. For example, the angle between the two can be 90° or close to 90°, such as 80° to 100°. The extension direction X of the current collector 21 refers to the overall orientation of the current collector 21 as X, but bending in other directions is allowed locally.

[0073] It should be noted that the acquisition of PL in this application can refer to the PL brightness of the entire surface of the solar cell under test without shading and irradiated with preset light, or to forming an irradiation area with a width of W, and stitching the above-mentioned local photoluminescence image 61 to obtain the photoluminescence image of the entire surface of the solar cell under test in the open circuit state, and obtaining the PL from the photoluminescence image of the entire surface of the solar cell under test in the open circuit state.

[0074] Step S4, EL1 acquisition step, acquire the electroluminescence value EL1 of the solar cell under test when it is irradiated by the first preset light in the open circuit state.

[0075] As mentioned above, after obtaining the local electroluminescence images 62 excited by the induced current on both sides of the irradiated area in the direction of movement, this step is to stitch the above-mentioned local electroluminescence images 62 to obtain the electroluminescence image of the entire surface of the solar cell under test in the open circuit state, and to obtain EL1 from the electroluminescence image of the entire surface of the solar cell under test in the open circuit state.

[0076] The open-circuit state of the solar cell mentioned in this application refers to the state in which the solar cell voltage is at its highest and the current is zero.

[0077] The execution order of steps S101 and S4 is not limited here. For example, S101 can be executed first, followed by S4, or S4 can be executed first, followed by S101.

[0078] Step S5, equivalent voltage drop acquisition step: Based on PL11 and EL1, determine the first equivalent voltage drop of the solar cell under test. .

[0079] In this application, for determining via PL11 and EL1 The method is not limited. For example, one method could be: V t This represents the thermal voltage of the solar cell at 25°C. Specifically, for each pixel in the emission image of the solar cell under test, PL11 and the corresponding EL1 are used to calculate the thermal voltage of that pixel. Then, all pixels of the emission image of the solar cell under test are analyzed. The average value is then calculated to obtain the value of the solar cell under test. .

[0080] In some embodiments, before step S101 or step S4, the method may further include: dividing the solar cell under test into multiple regions, where multiple refers to three or more regions. The PL11 acquisition step includes: for each region, acquiring the PL11 of the region under the first preset illumination in the open-circuit state of the solar cell under test; the EL1 acquisition step includes: for each region, acquiring the electroluminescence value EL1 of the region under the first preset illumination in the open-circuit state of the solar cell under test; the equivalent voltage drop acquisition step includes: for each region, determining the first equivalent voltage drop of the solar cell under test in that region based on the PL11 and EL1 corresponding to that region. Calculate the first equivalent voltage drop across all regions of the solar cell under test. The average value. Specifically, relative to each pixel as described above, dividing the solar cell under test into regions can significantly reduce the first equivalent voltage drop. This reduces the computational workload, improves testing efficiency, and has virtually no impact on testing accuracy.

[0081] For example, still using The equivalent voltage drop is calculated. Specifically, for each region of the emission image of the solar cell under test, PL11 and the corresponding EL1 are used to calculate the voltage drop of that pixel. Then, the emission image of all areas of the solar cell under test is obtained. The average value is then calculated to obtain the value of the solar cell under test. .

[0082] Step S6, the target series resistance determination step, involves determining the first equivalent voltage drop of the solar cell under test. Substituting the preset relationship of series resistance corresponding to the cell type of the solar cell under test, the target series resistance Rs of the solar cell under test is calculated; wherein, the preset relationship of series resistance is: Rs = X × +Q; X and Q are both constants.

[0083] Specifically, the first equivalent voltage drop of the solar cell under test The voltage drop is caused by the internal resistance of the solar cell under test. The preset relationship of the series resistance corresponding to this type of cell is obtained by fitting multiple equivalent voltage drops of multiple solar cells of this type, which can improve the accuracy of the series resistance test.

[0084] In some embodiments, the method may further include, prior to step S6, a series resistance preset formula determination step; for multiple solar cells of the same cell type as the solar cell under test: using a contact testing method to obtain the contact series resistance of each solar cell; obtaining PL3 of each solar cell under the first preset illumination in the open-circuit state; obtaining the electroluminescence value EL2 of each solar cell under the first preset illumination in the open-circuit state; determining the second equivalent voltage drop of each solar cell based on PL3 and the electroluminescence value EL2; and fitting the series resistance preset formula corresponding to the cell type of the solar cell under test, as well as X and Q in the series resistance preset formula corresponding to the cell type of the solar cell under test, based on the multiple contact short-circuit current densities and multiple second equivalent voltage drops. The multiple solar cells of the same cell type as the solar cell under test mentioned in this application refer to multiple other solar cells of the same cell type as the solar cell under test. Here, "multiple" can mean hundreds or even thousands of other solar cells. The series resistance preset formula obtained by fitting is more accurate in calculating the target series resistance of the solar cell under test, which can improve the accuracy of the series resistance test.

[0085] It should be noted that for multiple solar cells of the same type as the solar cell under test, the methods for obtaining PL3, electroluminescence value EL2 and the second equivalent voltage drop are the same or similar to the methods for obtaining and determining PL11, EL1 and the first equivalent voltage drop mentioned above. To avoid repetition, they will not be described again.

[0086] In some embodiments, the test method further includes a test step for the conversion efficiency of the solar cell under test. The aforementioned step S1 may include step S102, and the test method may further include the following steps S7 to S11.

[0087] Step S102, for at least three second preset light intensities: obtain PL12 of each second preset light intensity under the open-circuit state of the solar cell under test.

[0088] The second preset light intensity here corresponds to the light intensity corresponding to the resistance value at the maximum power point of the solar cell type under test. In other words, the second preset light intensity encompasses the light intensity corresponding to the resistance value at the maximum power point of the solar cell type under test. In some embodiments, if the solar cell under test is a crystalline silicon solar cell, the second preset light intensity includes at least 0.03 sun to 0.07 sun. Specifically, for a crystalline silicon solar cell, the resistance value at the maximum power point is 0.05 sun and its vicinity. Therefore, in this application, for crystalline silicon solar cells, the second preset light intensity includes at least 0.03 sun to 0.07 sun, corresponding to the maximum power point of the solar cell type under test, which can improve the accuracy of conversion efficiency testing. For example, the second preset light intensity can be 0.03 sun, 0.04 sun, 0.05 sun, 0.06 sun, or 0.07 sun.

[0089] It should be noted that the second preset illumination for solar cells other than crystalline silicon solar cells can be determined based on the light intensity corresponding to the resistance value of the maximum power point corresponding to the cell type of the solar cell. The second preset illumination only needs to cover the light intensity corresponding to the resistance value of the maximum power point corresponding to the cell type of the solar cell under test, which will not be elaborated further in this application.

[0090] Step S7, for at least three second preset light intensities: equivalent current density determination step, based on the short-circuit current density of the solar cell under test, determines the equivalent current density corresponding to each second preset illumination.

[0091] The method for determining the equivalent current density here is not limited. For example, the equivalent current density of the solar cell under test at each second preset light intensity can be calculated using the formula J = Jsc × (1 - second preset light intensity). In some embodiments, the short-circuit current density Jsc of the solar cell under test here is the target short-circuit current density of the solar cell under test obtained in step S3 above, thereby reducing the amount of calculation. It should be noted that the short-circuit current density of the solar cell under test here can also be the series resistance of the solar cell under test obtained again by a non-contact method, and this is not limited.

[0092] Step S8, for at least three second preset light intensities: first voltage determination step, determine the equivalent voltage under each second preset light intensity irradiation according to PL12.

[0093] The method for determining the equivalent current density here is not limited. For example, it can be done through... -[ It is determined that c is a constant, which can be calculated by comparing the contact voltage results of the solar cell of the cell type under test with the PL brightness image. More specifically, for each pixel or each region of the emission image of the solar cell under test under the second preset light intensity, the equivalent voltage of each pixel or each region can be obtained. Then, the equivalent voltage of all pixels or all regions is averaged to obtain the equivalent voltage of the solar cell under test under the second preset light intensity. As mentioned above, compared with pixels, this application uses regions to reduce the amount of calculation and improve the testing efficiency.

[0094] Step S9, Partial IV Curve Determination Step: Based on the equivalent current density and equivalent voltage corresponding to the solar cell under test for the at least three second preset light intensities, a partial IV curve of the solar cell under test is plotted.

[0095] This step involves plotting a partial IV (current-voltage) curve for the solar cell under test based on the equivalent current density and equivalent voltage corresponding to at least three second preset light intensities. Since the PL12 and equivalent current density are determined under this second preset illumination, and this second preset illumination covers the light intensity corresponding to the resistance value at the maximum power point of the solar cell type under test, this partial IV curve covers the maximum power point of the solar cell under test.

[0096] Step S10, the first conversion efficiency determination step, determines the maximum quasi-conversion efficiency of the solar cell under test based on a partial IV curve of the solar cell under test.

[0097] The maximum quasi-conversion efficiency of the solar cell under test is determined from a partial IV curve. As mentioned earlier, the partial IV curve covers the maximum power point of the solar cell under test, therefore the maximum quasi-conversion efficiency can be determined from this partial IV curve.

[0098] Step S11, Target Conversion Efficiency Determination Step: Determine the target conversion efficiency of the solar cell under test based on its series resistance and maximum quasi-conversion efficiency.

[0099] As mentioned earlier, series resistance can cause voltage drop in the solar cell under test, which may affect its conversion efficiency. Therefore, by using the aforementioned partial IV curve to determine the maximum quasi-conversion efficiency of the solar cell under test, and combining this with the series resistance, the conversion efficiency of the solar cell under test can be obtained. This eliminates the influence of series resistance on the conversion efficiency and improves the accuracy of the conversion efficiency obtained from the test.

[0100] In some embodiments, the series resistance of the solar cell under test can be the target series resistance Rs of the solar cell under test determined in step S6 above, which can reduce the amount of calculation and improve the detection efficiency. It should be noted that the series resistance of the solar cell under test can also be the series resistance of the solar cell under test obtained again by non-contact method, and there is no limitation on this.

[0101] In some embodiments, step S11 may include: substituting the series resistance R1 and the maximum quasi-conversion efficiency pEta of the solar cell under test into a preset conversion efficiency formula corresponding to the cell type of the solar cell under test, to calculate the target conversion efficiency Eta of the solar cell under test; wherein, the preset conversion efficiency formula corresponding to the cell type of the solar cell under test is: Eta = (pEta - Y × R1) × T + Z, where Y, T, and Z are all constants. In the preset conversion efficiency formula corresponding to the cell type of the solar cell under test, pEta is the efficiency unaffected by the series resistance of the solar cell under test, while Y × R1 is the part of the efficiency of the solar cell under test affected by the series resistance. Therefore, the efficiency of the solar cell under test can be obtained by subtracting the two. Furthermore, this preset formula is obtained by fitting the conversion efficiency and series resistance obtained from contact measurements of multiple solar cells of the cell type of the solar cell under test, and has universality for all solar cells of the cell type of the solar cell under test, which can improve the accuracy of conversion efficiency testing. Here, "multiple" refers to hundreds or even thousands of solar cells.

[0102] In some embodiments, the testing method may further include a step of determining a preset conversion efficiency formula corresponding to the cell type of the solar cell under test. Specifically, this may involve: for at least three second preset light intensities, multiple solar cells of the cell type of the solar cell under test: using a contact testing method to obtain the contact conversion efficiency of each solar cell; obtaining the PL4 of each solar cell under each second preset light irradiation in the open-circuit state; determining the equivalent current density corresponding to each second preset light irradiation based on the short-circuit current density of each solar cell; determining the equivalent voltage under each second preset light irradiation for each solar cell based on the PL4; plotting a partial IV curve for each solar cell based on the equivalent current density and equivalent voltage corresponding to the solar cells at at least three second preset light intensities; determining the maximum quasi-conversion efficiency of each solar cell based on the partial IV curve; and fitting a preset conversion efficiency formula corresponding to the cell type of the solar cell under test, as well as Y, T, and Z in the preset conversion efficiency formula corresponding to the cell type of the solar cell under test, based on the series resistance and maximum quasi-conversion efficiency of the multiple solar cells. The relationship obtained by fitting the above parameters of multiple solar cells to the cell type of the solar cell under test is universally applicable to solar cells of the cell type under test, which can improve the accuracy of conversion efficiency testing.

[0103] This application also provides a testing system for solar cells, which may include: a photoluminescence tester for acquiring a first PL brightness PL1 of the solar cell under test; the solar cell includes a first surface and a second surface opposite each other in the thickness direction of the solar cell; an optical detector for acquiring a first color value M of the first surface and / or the second surface of the solar cell under test; and a target short-circuit current density determination module for calculating the target short-circuit current of the solar cell under test based on the PL1 and M of the solar cell under test.

[0104] In some embodiments, the optical detector can be a camera, such as an industrial camera or other camera capable of acquiring color values.

[0105] The solar cell testing system of this application can implement any of the aforementioned solar cell testing methods and achieve the same or similar beneficial effects. The two can be referred to each other. In order to avoid duplication, they will not be described again.

[0106] This application also provides a computer-readable storage medium that, when the instructions / programs in the computer storage medium are executed by a processor, enables the execution of the steps of the various embodiments of the above-described solar cell testing method.

[0107] The following specific examples further illustrate this application.

[0108] Example 1 The first PL brightness PL1 is acquired in the open-circuit state of the solar cell under test at a range of 0.03 sun (standard solar intensity) to 0.07 sun. Since PL1 corresponds to 0.03 sun to 0.07 sun, it can also correspond to the aforementioned PL11 and PL12. In this step, a color image containing the background of the solar cell under test and at least the edge region of the light-facing surface of the solar cell under test can be acquired; a light emission image containing the background of the solar cell under test and the light emission image of the solar cell under test in the open-circuit state can be acquired; based on the color image, the background of the solar cell under test is removed from the light emission image of the solar cell under test containing the background to obtain the light emission image of the solar cell under test in the open-circuit state; and then the first PL brightness is acquired based on the light emission image. Simultaneously, the light emission image of the solar cell under test containing the background is a light emission image of the light-facing surface of the solar cell under test containing the background, and includes the edge and corner positions of the solar cell under test.

[0109] Obtain the RGB values ​​of the light-facing surface of the solar cell under test, convert the RGB values ​​to HSV values, and then... The HSV value is converted into the first color value of the light-facing surface of the solar cell under test, where A1 is 1.2 and B1 and D1 are both 0.

[0110] Based on PL1 and M of the solar cell under test, and Jsc = (PL1 - E × M) × F + G, the target short-circuit current density Jsc of the solar cell under test is calculated.

[0111] EL1 was obtained when the solar cell under test was exposed to 0.03 sun to 0.07 sun in an open-circuit state. Based on PL1 and EL1, determine the first equivalent voltage drop of the solar cell under test. . The first equivalent voltage drop of the solar cell under test Substitute the preset relationship Rs=X× corresponding to the series resistance of the solar cell under test. +Q, the target series resistance Rs of the solar cell under test is calculated.

[0112] Based on the short-circuit current density Jsc of the solar cell under test, determine the equivalent current density corresponding to each illumination within the range of 0.03sun to 0.07sun.

[0113] The equivalent voltage under each second preset light intensity irradiation is determined based on the aforementioned PL1.

[0114] Based on at least three light intensities between 0.03sun and 0.07sun, plot the partial IV curves of the solar cell under test corresponding to the equivalent current density and equivalent voltage, respectively.

[0115] Based on a partial IV curve of the solar cell under test, the maximum quasi-conversion efficiency of the solar cell under test is determined.

[0116] Based on the series resistance Rs, maximum quasi-conversion efficiency pEta, and Eta = (pEta - Y × R1) × T + Z of the solar cell under test, the target conversion efficiency Eta of the solar cell under test is determined.

[0117] In Example 1, the above-described test parameters of the solar cell under test were measured. Compared to contact-based cell testing, the test time was reduced by approximately 20.5%, the breakage rate decreased by 86.7%, and the test stability improved by 63.5%. The absolute value of the difference between the test results and the contact-based measurement results is less than 5% of the larger of the two, indicating that the measurement results are more accurate. The test stability of Example 1 refers to the percentage of 100 solar cells where, for each of the 100 solar cells under test, at least three tests were conducted using the method described in Example 1, and the absolute value of the maximum deviation of the test results was less than 5% of the average value of the test results.

[0118] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0119] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not 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 this application.

[0120] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0121] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0122] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for testing solar cells, characterized in that, include: The first PL brightness acquisition step is to acquire the first PL brightness PL1 of the solar cell under test in the open-circuit state. In the thickness direction of the solar cell, the solar cell includes opposing first and second surfaces; The first color value acquisition step involves acquiring the first color value M of the first surface and / or the second surface of the solar cell under test. The target short-circuit current density determination step involves calculating the target short-circuit current density of the solar cell under test based on PL1 and M.

2. The test method for solar cells according to claim 1, characterized in that, The steps for determining the target short-circuit current density include: Substitute the PL1 and M of the solar cell under test into the preset relationship of short-circuit current density corresponding to the cell type of the solar cell under test, and calculate the target short-circuit current density Jsc of the solar cell under test. The preset relationship for the short-circuit current density is: Jsc = (PL1 - E × M) × F + G; where E, F, and G are all constants. Before the step of determining the target short-circuit current density, the method further includes: a step of determining a preset relationship for short-circuit current density. For multiple solar cells of the cell type of the solar cell under test: The contact short-circuit current density of each solar cell was obtained using a contact-type test method. Obtain the second PL brightness PL2 of each solar cell in the open-circuit state; Obtain the second color value of the first and / or second surface of each solar cell; Based on multiple contact-type short-circuit current densities, multiple second PL brightness values, and multiple second color values, a preset relationship for the short-circuit current density corresponding to the cell type of the solar cell under test is obtained by fitting, as well as E, F, and G in the preset relationship for the short-circuit current density corresponding to the cell type of the solar cell under test.

3. The test method for solar cells according to claim 1, characterized in that, The first color value acquisition step includes: Obtain the RGB values ​​of the first and / or second surfaces of the solar cell under test, convert the RGB values ​​to HSV or Lab values, and then... Convert the HSV value to the first color value, where A1, B1, and D1 are all constants greater than or equal to 0, and A1 > D1 ≥ B1; or, according to The Lab value is converted into the first color value; A2, B2 and D2 are all constants greater than or equal to 0, and D2≥B2>A2.

4. The test method for solar cells according to claim 1, characterized in that, The first PL brightness acquisition step includes: acquiring the PL11 of the solar cell under test in an open-circuit state when it is illuminated by a first preset illumination; the first preset illumination is 0.01 to 0.2 standard solar irradiance. The method further includes: The EL1 acquisition step involves acquiring the electroluminescence value EL1 of the solar cell under test when it is exposed to the first preset light in an open-circuit state. The equivalent voltage drop acquisition step involves determining the first equivalent voltage drop of the solar cell under test based on PL11 and EL1. ; The target series resistance determination step involves determining the first equivalent voltage drop of the solar cell under test. Substitute the preset relationship of series resistance corresponding to the cell type of the solar cell under test into the formula to calculate the target series resistance Rs of the solar cell under test. The preset formula for the series resistance is: Rs = X × +Q; X and Q are both constants; Before the step of determining the target series resistance, the method further includes: a step of determining the preset relationship of series resistance; For multiple solar cells of the cell type of the solar cell under test: The contact series resistance of each solar cell was obtained using a contact-type testing method. Obtain PL3 under the first preset illumination when each solar cell is in an open-circuit state; Obtain the electroluminescence value EL2 of each solar cell under the first preset illumination when it is in the open-circuit state; Based on PL3 and EL2, determine the second equivalent voltage drop of each solar cell; Based on multiple contact short-circuit current densities and multiple second equivalent voltage drops, a preset relationship for the series resistance corresponding to the cell type of the solar cell under test is obtained by fitting, as well as X and Q in the preset relationship for the series resistance corresponding to the cell type of the solar cell under test.

5. The test method for solar cells according to claim 4, characterized in that, Before the first PL brightness acquisition step, the method further includes: dividing the solar cell under test into multiple regions; The first PL brightness acquisition step includes: for each region, acquiring the PL11 of the region under the first preset illumination when the solar cell under test is in an open-circuit state; The EL1 acquisition step includes: for each region, acquiring the electroluminescence value EL1 of the region under the first preset illumination when the solar cell under test is in an open-circuit state; The equivalent voltage drop acquisition step includes: for each region, determining the first equivalent voltage drop of the solar cell under test based on the PL11 and EL1 corresponding to the region. ; Calculate the first equivalent voltage drop across all regions of the solar cell under test. The average value.

6. The test method for solar cells according to claim 1, characterized in that, The first PL brightness acquisition step includes: for at least three second preset light intensities: acquiring PL12 when the solar cell under test is irradiated by each second preset light intensity in the open-circuit state; The method further includes: The equivalent current density determination step involves determining the equivalent current density corresponding to each second preset illumination based on the short-circuit current density of the solar cell under test. The first voltage determination step involves determining the equivalent voltage under each second preset light intensity irradiation based on PL12. The IV curve determination step involves plotting a portion of the IV curve of the solar cell under test based on the equivalent current density and equivalent voltage corresponding to the at least three second preset light intensities. The first conversion efficiency determination step involves determining the maximum quasi-conversion efficiency of the solar cell under test based on a portion of its IV curve. The target conversion efficiency determination step involves determining the target conversion efficiency of the solar cell under test based on its series resistance and maximum quasi-conversion efficiency.

7. The test method for solar cells according to claim 6, characterized in that, The short-circuit current density of the solar cell under test is the target short-circuit current density of the solar cell under test; and / or, The series resistance of the solar cell under test is the target series resistance Rs of the solar cell under test; and / or, The solar cell under test is a crystalline silicon solar cell, and the second preset light intensity includes at least 0.03 to 0.07 standard solar intensities.

8. The test method for solar cells according to claim 6, characterized in that, The steps for determining the target conversion efficiency include: Substitute the series resistance R1 and the maximum quasi-conversion efficiency pEta of the solar cell under test into the preset conversion efficiency relationship corresponding to the cell type of the solar cell under test, and calculate the target conversion efficiency Eta of the solar cell under test. The preset formula for the conversion efficiency corresponding to the cell type of the solar cell under test is: Eta = (pEta - Y × R1) × T + Z, where Y, T and Z are all constants; Before the step of determining the target conversion efficiency, the method further includes: For at least three second preset light intensities, the cell type of the solar cell under test includes multiple solar cells: The contact conversion efficiency of each solar cell was obtained using a contact testing method. Obtain PL4 for each second preset illumination under the open-circuit state of each solar cell; Based on the short-circuit current density of each solar cell, determine the equivalent current density corresponding to each second preset illumination. For each solar cell, the equivalent voltage under each second preset light intensity irradiation is determined according to PL4; For each solar cell, a partial IV curve of the solar cell is plotted based on the equivalent current density and equivalent voltage corresponding to at least three second preset light intensities. For each solar cell, the maximum quasi-conversion efficiency of the solar cell is determined based on a portion of its IV curve. Based on the series resistance and maximum quasi-conversion efficiency of multiple solar cells, a preset conversion efficiency formula corresponding to the cell type of the solar cell under test is obtained by fitting, as well as Y, T, and Z in the preset conversion efficiency formula corresponding to the cell type of the solar cell under test.

9. The test method for solar cells according to any one of claims 1 to 8, characterized in that, In the PL brightness acquisition step: the PL brightness of the solar cell under irradiation of 0.01 to 0.2 standard solar intensities is acquired.

10. The test method for solar cells according to any one of claims 1 to 8, characterized in that, Before acquiring the PL brightness, the following steps are also included: Acquire a color image containing the background where the solar cell is located, and at least the edge regions of the first and / or second surfaces of the solar cell; Acquire a background containing the solar cell and a light-emitting image of the solar cell in an open-circuit state, the light-emitting image including a sub-light-emitting image of the solar cell in the open-circuit state; Based on the color image, the portion of the battery edge region in the luminescent image that was mistakenly identified as the background of the solar cell is added to the sub-luminescent image to obtain the luminescent image of the solar cell in the open-circuit state; The PL brightness acquisition includes: acquiring the PL brightness of the solar cell in the open-circuit state based on the emission image of the solar cell.

11. A testing system for solar cells, characterized in that, include: A photoluminescence meter is used to obtain the first PL brightness PL1 of the solar cell under test. In the thickness direction of the solar cell, the solar cell includes opposing first and second surfaces; An optical inspection instrument is used to acquire the first color value M of the first surface and / or the second surface of the solar cell under test; The target short-circuit current density determination module is used to calculate the target short-circuit current density of the solar cell under test based on PL1 and M.

12. A computer-readable storage medium having a computer program / instructions stored thereon, characterized in that, When executed by a processor, the computer program / instructions implement the test method for the solar cell as described in any one of claims 1 to 10.

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