Solar cell test procedure, solar cell production procedure, solar cell test system and solar cell production system
Patent Information
- Application Number
- EP2023740942
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-06-28
- Filing Date
- 2023-06-27
- Publication Date
- 2025-05-07
Smart Images
Figure 1.1
Abstract
Description
[0001] Title:
[0002] Solar cell testing process, solar cell production process, solar cell testing facility and solar cell production facility
[0003] Description:
[0004] The invention relates to a solar cell testing process, a solar cell production process, a solar cell testing system and a solar cell production system.
[0005] In modern solar cell production facilities, solar cells are subjected to a series of tests and measurements following production. These measurements serve, on the one hand, as quality assurance, as poor or defective solar cells are eliminated. On the other hand, the results of such tests can be used to sort the manufactured solar cells, particularly based on their performance or efficiency. This sorting process is also known as binning. The measurement of a solar cell takes place immediately at the end of a production line, in what is known as end-of-line cell testing. This has the advantage that the solar cells do not have to be transported to another location, and perhaps even packaged beforehand, for testing there.
[0006] Currently, solar cells are 100% contacted at the end of production using IV sun simulators, so-called flashers, and measured according to standards and converted to standardized values under standard test conditions (STC). This is referred to as 100% STC testing. The measurement systems used for this are complex, expensive, and their throughput can hardly be accelerated any further. STC testing of the IV characteristic curve (according to IEC 60904) involves standardized illumination of each solar cell with a standard light spectrum (AM 1.5 G). Under AM 1.5 G light conditions, irradiation with one sun is defined as a radiance of 100 mW / cm². 2During this irradiation, the current-voltage characteristic (IV curve or simply IV curve) is measured to determine, among other things, the electrical performance of the solar cell under standard illumination. Illumination according to a standard spectrum and intensity can only be achieved using relatively expensive LED or xenon lighting units, due to the high demands on intensity, spectrum, stability, and homogeneity.
[0007] EP 2 823 899 A1 discloses a method and a binning device for sorting solar cell wafers in corresponding containers based on their characterization. For this purpose, the solar cells are tested and measured using various inspection devices. The tests serve to detect damage to the solar cell wafers, determine their respective color, and determine their optical and electronic properties.
[0008] EP 1 647 827 A1 describes a test system for solar cells comprising an optical and an electrical test device arranged along a conveyor belt system. Driven by the conveyor belt system, the solar cells pass through the test devices and are tested and measured both optically and electrically.
[0009] The object of the invention is to reduce the investment costs per manufactured solar cell and to increase the throughput of end-of-line cell testing.
[0010] The object is achieved according to the invention by a solar cell testing process, a solar cell production process having the features of claim 1, by a solar cell production process having the features of claim 10, by a solar cell testing system having the features of claim 12, and by a solar cell production system having the features of claim 17. Advantageous developments of the invention are listed in the subclaims.
[0011] According to one aspect of the invention, a solar cell testing process is proposed in which each solar cell of a plurality of solar cells is subjected to a series of process steps of the solar cell testing process at the respective end of one or more production lines. A primary measurement method is carried out on each solar cell, and a primary measurement result is thus determined. The primary measurement result is then evaluated. The evaluation result indicates whether the solar cell can be classified or sorted into a predetermined sorting category based exclusively on the primary measurement result (positive evaluation result) or not (negative evaluation result). In other words, the evaluation determines whether it is sufficient to test the solar cell using the primary measurement method in order to subsequently sort it, i.e., to bin it.The sorting category is predetermined in that it is determined in advance which requirements the solar cell must meet in order to be sorted into this sorting category.
[0012] If the evaluation result is positive, the solar cell in question is classified or sorted into a sorting category in a next step based on the primary measurement result. If, however, the evaluation result is negative, a further measurement procedure is carried out on the solar cell in question, which will be referred to below as the secondary measurement procedure to distinguish it from the primary measurement procedure to which all solar cells are subjected. The result of the primary measurement procedure then produces a secondary measurement result for the solar cell, and based on this secondary measurement result, the solar cell can be classified or sorted into an associated sorting category. Optionally, in addition to the secondary measurement result, the previously determined primary measurement result can also be used to select the sorting category into which the solar cell is to be classified or sorted.
[0013] The invention is based on the idea of subjecting all solar cells to a primary measurement method, which can be simpler, cheaper, faster, and / or less damaging to the solar cell than the secondary measurement method, while only a smaller number of solar cells need to be subjected to the secondary measurement method. This results in correspondingly lower resources. Since fewer solar cells are subjected to the secondary measurement method, the secondary measurement method can also be designed much more complexly and include more, and possibly more complex, measurements than is usually the case if resource conservation must be considered for each solar cell.
[0014] In particular, a power value or efficiency of the solar cell can be determined based on the primary measurement result. A power value or efficiency of the solar cell can also preferably be determined from the secondary measurement result, i.e., in particular, from the IV characteristic curve.
[0015] The solar cell testing process is performed on substantially all of the solar cells produced. "Substantially" means that at most a negligible subset of solar cells compared to the total quantity of solar cells is not measured using the primary measurement method, for example, solar cells that are obviously defective, in particular, cracked or have scratches or color defects.
[0016] The primary measurement determines a primary measurement result for each solar cell. Multiple primary measurements can be performed on each solar cell, either in parallel or sequentially, using different primary measurement methods. Accordingly, multiple primary measurement results can be determined. It should be noted that the terms primary measurement and secondary measurement do not imply a temporal or other order between the measurements. For example, if solar cells are consistently in good condition but still need to be subjected to secondary measurements at regular intervals to recalibrate and / or monitor the system, the secondary measurement can alternatively be performed before the primary measurement. The term primary measurement refers to a set of first measurements, and the term secondary measurement refers to a set of second measurements.The primary measurement differs from the secondary measurement in that, of a set of solar cells under consideration, essentially all are subjected to the primary measurement and only a subset is subjected to both the primary measurement and the secondary measurement, namely those solar cells for which the evaluation result is negative.
[0017] The primary measurement result(s) and / or the secondary measurement result(s) may each comprise a key figure, a qualification, and / or a set of key figures or qualifications. In particular, the primary measurement result and / or the secondary measurement result may comprise a measurement curve, for example, a current-voltage (IV) measurement curve or a photoluminescence (PL) image, an electroluminescence (EL) image, or an infrared (IR) image.
[0018] The primary measurement method can expediently be a faster and / or more cost-effective measurement method than the secondary measurement method. In contrast, the secondary measurement method should preferably be designed such that it can be used to calibrate the primary measurement method. According to the invention, the secondary measurement method is therefore considered the normative or standard measurement method, while the primary measurement method serves as a faster and / or more cost-effective alternative to the secondary measurement method. Such calibration preferably always occurs when a solar cell has been subjected to both the primary measurement method and the secondary measurement method, thus providing a primary measurement result and a secondary measurement result.While the invention provides that all solar cells are tested using the primary measurement method and that a solar cell is only subjected to the secondary measurement method if the evaluation of the primary measurement result for this solar cell shows that there is insufficient information to clearly classify and appropriately sort this solar cell, it can be advantageous in some embodiments to subject solar cells to the secondary measurement method regardless of the evaluation result and / or the primary measurement result and / or even if the evaluation result is positive. The secondary measurement result determined from this can then be used to perform a calibration. This is particularly useful when the system is running well and the evaluation result is therefore predominantly positive. Such sporadic calibration, independent of or in the event of a positive evaluation result, ensures that the solar cell testing process is regularly calibrated.
[0019] Advantageously, after the secondary measurement method has been performed on the solar cell, the primary measurement method and / or the evaluation method are calibrated depending on the primary measurement result and the secondary measurement result. Calibration can preferably be performed to adapt or approximate the significance of the primary measurement result to that of the secondary measurement result. Calibration is then preferably performed regularly. Thus, according to a preferred embodiment, after the secondary measurement method has been performed on the solar cell, the primary measurement method and / or the evaluation method are calibrated depending on the primary measurement result and the secondary measurement result.During the calibration of the primary measurement method, the evaluation of the primary measurement result is adjusted in such a way that the characteristics of the solar cell derived from the primary measurement results essentially agree with the characteristics of the same solar cell derived from the secondary measurement results.
[0020] This makes it possible to draw conclusions about the secondary measurement results with a certain degree of accuracy using only the primary measurement results. For this purpose, parameters in the algorithms used to convert the primary measurement result into the characteristic value can be adjusted. In one expedient embodiment, the secondary measurement method comprises a contact-based measurement method. This means that the solar cell to be measured is electrically contacted for the measurement. The solar cell can then be illuminated or irradiated using a lighting device, with electrical quantities, in particular current and / or voltage, being recorded at the contact(s) during or after the irradiation. The recording can take place at a specific point in time or over a period of time. It is also possible to determine an average value of an electrical quantity over a specific period of time.For example, the current or voltage generated in the solar cell due to the illumination can be recorded over time. Alternatively or additionally, an electrical quantity can be adjusted using the contact, while simultaneously recording another electrical quantity at the contact. In this way, for example, a current-voltage characteristic (IV characteristic) can be determined. This can be done with or without illumination.
[0021] Preferably, the secondary measurement method is a current-voltage characteristic curve measurement in the dark and / or under the illumination of a solar simulator under standard test conditions (STC). Such STC measurements of the IV characteristic curve (according to IEC 60904) involve standardized illumination of the solar cell with a standard light spectrum (AM1.5G) and an irradiance of 1000 W / m 2and a solar cell temperature of 25°C. The current-voltage characteristic is measured to determine the electrical performance of the solar cell under standard lighting. Illumination with a standard spectrum and standard intensity can be achieved, for example, using LED or xenon lighting units, as the requirements for intensity, spectrum, stability, and homogeneity are high. Typically, the solar cell temperature present during the measurement is measured, and the electrical measured values of the solar cell are mathematically corrected to values of 25°C.
[0022] Preferably, the primary measurement method is faster and / or less expensive than the secondary measurement method. In particular, the primary measurement method does not require illumination according to standard test conditions (STC). The hybridization of cell measurements in such non-STC measurements and STC measurements enables increased throughput, especially when the non-STC measurements are contactless, as is the case with photoluminescence measurements, for example. The equipment technology for non-STC measurements is significantly more cost-effective, and higher measurement throughputs can be achieved.
[0023] The primary measurement method preferably comprises one or more luminescence measurements in which luminescence images of the solar cell surface are captured, in particular an electroluminescence measurement (EL measurement) and / or a photoluminescence measurement (PL measurement). In an electroluminescence measurement, the solar cell is contacted and excited by electrical signals, i.e. in particular by a current flow or an applied voltage. In a photoluminescence measurement, the solar cell is excited by irradiation, in particular laser irradiation. In both cases, the luminescence images can be captured using a camera. In this case, the camera can either capture the entire surface of a solar cell at once. Alternatively, it is possible to scan the solar cell surface in sections using the camera.
[0024] Luminescence measurements are in equilibrium within the excess charge carrier lifetime, which is approximately 1 millisecond (ms) or on the order of 1 ms. Hysteresis does not occur because the external sensing voltage is not changed over time. This even allows measurements on moving solar cells, so-called "on-the-fly" measurements, when local exposure times are in the range of a few milliseconds. Such luminescence measurements are thus at least an order of magnitude faster than power measurements derived from IV characteristics.
[0025] Preferably, a power value, a power class and / or an efficiency of the solar cell is determined from one or more luminescence images acquired from a solar cell and used as the basis for sorting. In addition, the characteristic parameters, in particular the short-circuit current Isc, the open-circuit voltage Voc and / or the fill factor, can also be determined. Preferably, the luminescence image or images are recorded or acquired in such a way that they contain relevant information in order to derive the power value, the power class and / or the efficiency of the solar cell, for example using resistance effects or if further primary measurements are required for this purpose. Preferably, the luminescence image(s) is / are evaluated for this purpose, for example by means of feature recognition using machine learning algorithms, in particular using artificial neural networks.
[0026] When taking luminescence images, the following options are possible:
[0027] • Acquisition of multiple luminescence images at different injection levels. This variant is applicable to both photoluminescence (PL) and electroluminescence (EL) measurements.
[0028] • Acquisition of multiple luminescence images at different illumination wavelengths. This variant is particularly applicable to photoluminescence (PL) measurements.
[0029] • Recording multiple luminescence images at different detection wavelength ranges.
[0030] • Recording of multiple luminescence images, each with front and / or back illumination (PL) and detection (PL, EL)
[0031] In a preferred embodiment, the primary measurement method comprises a contactless measurement method. A contactless measurement method has the advantage of saving contact time and reducing or avoiding mechanical stress on the solar cell under test. In addition to the photoluminescence measurement, this option includes a contactless measurement of the external quantum efficiency (EQE) ("PL-QE"), a contactless measurement of the series resistance, and the so-called "Suns-PL" measurement. All of these measurements have in common that signals are transmitted via the photoluminescence radiation, and only the type and manner of spatial, spectral, or temporal excitation of the radiation makes various properties accessible. Contactless measurements also support fast and damage-free measurement for the majority of solar cells produced. This is particularly advantageous for thin, large, and / or busbarless solar cells.This allows for increased throughput and eliminates the problematic contacting of busbarless solar cells.
[0032] In an advantageous development, the primary measurement method comprises an imaging measurement method and / or a non-imaging measurement method. An imaging measurement method can, in particular, be the aforementioned acquisition of luminescence images. A non-imaging measurement method is, in particular, the measurement of the solar cell using contacts, for example, the acquisition of an IV characteristic curve. A contactless, non-imaging measurement method is, for example, a contactless sheet resistance measurement, a contactless PL-QE measurement, a contactless series resistance measurement, or a contactless Suns-PL measurement.
[0033] As explained above, multiple primary measurements can be performed on each solar cell using different primary measurement methods. For example, a first primary measurement method can be a PL method and a second primary measurement method can be an EL method, which are applied consecutively to the same solar cell.
[0034] As explained above, it is advantageous to use a contactless measurement method as the primary measurement method. Furthermore, for high throughput and gentle solar cell transport, it is sensible to select measurement methods that measure the solar cells "on the fly" as the primary measurement method or as part of the primary measurement method. This avoids the time required for start-up / stop processes and / or handling of the solar cells. Examples of possible measurement methods include photoluminescence (PL), reflection, transmission, eddy current, or QSSPC – the latter ideally before metallization is applied to the solar cell. If individual measurement steps or measurement methods of the primary measurement method are to be carried out before the solar cell is completed, then cell-precise assignment is required, since a subsequent process step in solar cell production follows.Typically, this final process step involves metallizing the solar cell. Reflection and transmission measurements can be used to correct the PL measurement (wavelength corresponding to the PL signal).
[0035] According to a preferred development, the calibration of the primary measurement method and / or the evaluation method comprises the application of machine learning algorithms. For example, several pairs of a primary measurement result or an evaluation result and a secondary measurement result, which were previously determined on a solar cell, are made available to the algorithm. For each solar cell, one or more such result pairs are determined, which are used to train the algorithm, and model parameters of the algorithm are determined. The multiple result pairs can, in particular, be determined using different measurement parameters, for example, at different illuminance levels.Alternatively, for a solar cell with a pair of primary and secondary measurements, the secondary measurement can be used to determine a characterization of the solar cell, such as a power value and / or efficiency. The primary measurement and the resulting characterization can then be used to train the algorithm and determine the model parameters.
[0036] Subsequently, with the determined model parameters, the algorithm is able to determine an approximate result for the characterization of the solar cell, for example, a power value approximation and / or an efficiency approximation, in response to a primary measurement result as input. The better the algorithm functions, the smaller the gap between the approximate result and the characterization of the solar cell that would have been obtained if the solar cell had been measured using the secondary measurement method and the characterization of the solar cell had been derived from the resulting secondary measurement result.As explained above, recalibration is preferably performed at regular intervals, for example, at regular time intervals or after testing a certain number of solar cells or after the evaluation precision of the primary measurement has reduced. At least one solar cell is subjected to both the primary measurement and the secondary measurement. The (re)calibration minimizes the difference between the approximate result for the characterization of the solar cell derived from the primary measurement result using the algorithm and the characterization of the solar cell derived from the secondary measurement result.
[0037] If the primary measurement method includes one or more optical measurement methods, calibration factors are preferably adjusted or changed during calibration to track changes in the transfer of electrical properties to the optical recording technology, e.g., due to changes in the optical setup. Such optical measurement methods can, for example, include one or more of the following measurement methods: photoluminescence measurement methods, electroluminescence measurement methods, or infrared imaging of reverse-biased solar cells. These infrared images show the locations of local shunts.
[0038] Preferably, the calibration of the primary measurement method and / or the evaluation method includes the use of an artificial neural network. Thus, the algorithm explained above preferably includes the artificial neural network, and the model parameters are the parameters of the artificial neural network, in particular the weights of the artificial neural network. Alternatively or additionally, decision trees can also be used, for example, so-called "gradient boosted decision trees."
[0039] The artificial neural network preferably comprises a recurrent neural network (RNN) and / or a convolutional neural network (CNN), in which the activities of the neurons are calculated using discrete convolutions. The artificial neural network can comprise multiple layers, one, two, or more of which are convolved in this way. If it is an RNN, then it is a convolutional recurrent neural network.
[0040] The evaluation procedure expediently includes comparisons of the primary measurement result with fixed threshold values. Preferably, the threshold value(s) are the result, or at least partially the result, of a prediction using computer-assisted algorithms. An example of such a threshold value is the average image intensity in an electroluminescence measurement. The threshold value can also be the result of a prediction using computer-assisted algorithms. For example, solar cells that are definitely poor or definitely excellent can be classified or sorted immediately, while all remaining solar cells are subjected to a detailed IV measurement.
[0041] Additionally or alternatively, artificial intelligence (AI) methods are preferably used to design the evaluation procedures. In particular, machine learning algorithms and / or artificial neural networks can be used.
[0042] To monitor fixed limit values or for the purpose of self-learning, solar cells can be sporadically examined in detail using the secondary measurement method. This allows for refinement of the selection criteria, training of the machine learning system, and dynamic adaptation of the selection process to a production or material quality that is not 100% consistent. Furthermore, the comprehensive results of solar cells sporadically measured using the secondary measurement method can provide in-depth insight into ongoing solar cell production without the need for a complex separate analysis. The secondary measurement method can be performed in a separate measurement path that includes one or more measuring points or along which several secondary measuring devices are arranged. The measuring points or secondary measuring devices can be operated in parallel, in series, or as a combination of parallel and serial arrangements.The arrangement depends on how frequently the secondary measurement method has to be used and how long the secondary measurement method lasts.
[0043] It is also possible for multiple production lines, each equipped with a primary measurement device, particularly a flasher, to select the corresponding solar cells according to the primary measurement method and further characterize them in a shared, separate measurement path. Thus, each sub-line of a solar production plant has a primary measurement device and a different (e.g., smaller) number of separate measurement paths for secondary measurement. Depending on the requirements, the number of parallel primary measurement devices and the number of secondary measurement devices or separate measurement paths for the secondary measurement methods can be adapted to the measurement requirements and the associated throughput.
[0044] If the primary measurement method is not contactless or takes a long time compared to the cycle time of the solar cell test system, it may be useful to perform the primary measurement method in parallel on several cells, similar to a measurement of split solar cells, for example half cells or third cells. In this case, for example, several (split) solar cells are transported simultaneously to several contacting units (one contacting unit for several sub-cells) and characterized simultaneously or quasi-simultaneously. This contacted characterization can also comprise several contacting measurement methods, for example the measurement of the IV characteristic curve and an EL measurement, or both contacting measurement methods and contactless measurement methods. According to a preferred embodiment, the primary measurement method or a partial measurement method of the primary measurement method is carried out before a manufacturing step of the solar cell.For example, it may be provided that a primary measurement procedure or a sub-procedure of the primary measurement procedure is carried out before a final annealing step. In the latter case, a further sub-procedure of the primary measurement procedure can be carried out after or immediately after the final annealing step.
[0045] Depending on the chronological distribution of the solar cells within the solar cell test facility or the solar cell production facility, in particular depending on the distribution of the solar cells intended for secondary measurement and the resulting required additional secondary measurements in separate measurement paths, it is possible that a backlog occurs in front of one or more of the secondary measuring devices, i.e. that solar cells accumulate in front of the secondary measuring devices. Such backlogs can also occur behind one or more secondary measuring devices. To avoid or at least reduce this backlog, it may be advisable to install a solar cell buffer at each affected location in the facility. Thus, in an advantageous embodiment, the solar cell is held in a solar cell buffer before or after the secondary measurement process is carried out.Accordingly, the solar cell testing system can have the solar cell buffer before or after the secondary measuring device, or alternatively, the solar cell buffer can be provided as part of the secondary measuring device. The solar cell buffer(s) is / are designed to hold a plurality of solar cells before they are fed to the secondary measuring device or the sorting system. The solar cell buffer can be implemented in the form of a solar cell stack or a lift system similar to a paternoster.
[0046] To achieve high throughput at the primary measurement device and / or at the
[0047] To achieve this, it may also be useful to keep the measurement conditions constant in the primary and / or secondary measurement devices to reduce time delays caused by turn-on / turn-off effects. For example, the light level could be kept constant on the measurement device where the IV characteristic is measured to save settling time.
[0048] By outsourcing time-consuming measurements to the secondary measurement process, possibly even to a secondary measurement device in a separate measurement path, and accelerating the primary measurement process, time is gained. This allows the secondary measurement processes to be more complex than is typical in previous test procedures. In other words, additional measurements can be performed on the few solar cells that undergo the secondary measurement process, beyond the scope of end-of-line measurements used in current production lines, thus yielding additional data and insights without reducing the solar cell throughput of the solar cell test facility or solar cell production facility.
[0049] For example, the secondary measurement method may include one or more of the following measurement methods:
[0050] Determination of the cell's bifaciality factor. For a quick measurement, the measurement is preferably performed only on the front side at an irradiation level of 1.3 suns. The bifaciality factor is preferably checked continuously, but preferably sporadically. Bifaciality can be determined particularly at different intensities.
[0051] Determining the quality of the backside passivation by illuminating the backside, for example using UV radiation.
[0052] Reverse-biased EL (REBEL) to identify defects at grain boundaries.
[0053] Detection or prediction of degradation phenomena caused for example by iron-boron, PID (potential induced degradation), LeTID (light- and elevated temperature-induced degradation) or the like.
[0054] Measurement of EQE (External Quantum Efficiency) or pseudo EQE, EL and / or PL at different injection levels.
[0055] Suns-Voc measurements; Here, the light intensity is gradually increased, e.g., from zero to one sun. At each intensity level, Jsc and Voc are measured. These values yield an IV characteristic curve adjusted for the solar cell's series resistance.
[0056] In a system that has been running smoothly, essentially all solar cells are measured using the primary measurement method, while only a small portion of the manufactured or measured solar cells are also subjected to the secondary measurement method. This portion reaches the value of well less than 5% or 1%, preferably during normal operation after a start-up phase. In other words, during initial operation, after a product change, after a process change, after a material change, and / or after a longer break, in particular a testing break or production break, a basic calibration or basic modeling is first carried out. During this basic calibration, a large portion of manufactured solar cells is initially measured using both the primary measurement method and the secondary measurement method until the sorting precision of the primary measurement method meets the specification.The subset here is therefore very large and is preferably close to or at 100% at the beginning.
[0057] Preferably, a basic calibration is provided, which preferably takes place during a start-up or during a new or renewed commissioning of the solar cell production process and / or is repeated at regular intervals, for example weekly. Such a basic calibration or basic modeling is preferably carried out using sufficiently extensive and representative primary measurements and secondary measurements in order to obtain training data sets and calibration models for the calibration. For this purpose, initially a high proportion of the manufactured solar cells is preferably subjected to both the primary measurement and the secondary measurement, so that the subset is very high, preferably more than 90% or almost 100%. A calibration model is preferably generated using a training data set.
[0058] After such a start-up phase, the solar cell production process preferably transitions to continuous operation, during which recalibration can be performed regularly or sporadically based on the secondary measurement results. During recalibration, changes are made to model parameters that are used for the interpretation of the primary measurement results and the subsequent classification and sorting of the measured solar cells. Recalibration may be necessary because many processes within solar cell production are not long-term stable. This can be due, for example, to chemical solutions being used up, raw materials from different batches being used, ambient conditions in the production hall being subject to fluctuations, and the like.
[0059] According to one aspect of the invention, a solar cell production process is proposed in which solar cells are manufactured and subsequently subjected individually or in groups to a solar cell testing process according to one of the embodiments explained herein. Preferably, the solar cells are manufactured continuously and also continuously subjected to the test or measurement method explained below. For example, the manufactured solar cells can be tested in the order of their manufacture. The group of manufactured solar cells referred to as the "multiplicity of solar cells" can also be solar cells manufactured within a period of time, for example, within one hour, one day, or one week.
[0060] According to an advantageous embodiment of the solar cell production process, after the primary measurement method has been performed on the solar cell, the solar cell is subjected to a process step for completing and / or modifying the solar cell, in particular an annealing step. In other words, this solar cell is tested / measured using the primary measurement method before the solar cell is completed. Alternatively, the solar cell can be subjected to the primary measurement method before a modification step is performed. For example, it may be advantageous to perform the step of solar cell contacting or solar cell metallization only after the primary measurement method has been performed or after a partial measurement method of the primary measurement method has been performed.If a first primary measurement method and a second primary measurement method take place before and after an annealing step, then the effect of the annealing step can be precisely documented from the respective partial results determined in these two primary measurement methods.
[0061] According to a further aspect of the invention, a solar cell testing system is proposed. All embodiments described above or below in connection with the solar cell testing process can be implemented accordingly in the solar cell testing system.
[0062] According to a further development, the solar cell test system comprises an additional primary measuring device and a solar cell distribution system. The solar cell distribution system is designed to transport solar cells selectively from the primary measuring device or from the additional primary measuring device to the secondary measuring device.
[0063] A distribution system, for example, comprising robotic arms and / or conveyor belts, can ensure that all solar cells reach the primary measuring device and those solar cells requiring a secondary measurement reach the secondary measuring device. For this purpose, the secondary measuring device can be arranged along a separate measuring path, which differs from a measuring path along which all solar cells are moved from the primary measuring device to the sorting device. In other words, the primary measuring device and the secondary measuring device are located on different measuring paths, in particular parallel to each other, along which the solar cells are each moved to reach the sorting device.
[0064] Alternatively or cumulatively, the system can be designed such that all solar cells produced pass through the primary measuring device and the secondary measuring device, but the secondary measuring device is controlled such that only those solar cells requiring a secondary measurement are also measured using the secondary measurement method. In this case, the secondary measuring device can be arranged along a measurement path along which all solar cells are moved from the primary measuring device to the sorting device. In other words, the primary measuring device and the secondary measuring device are located on a common measurement path along which all solar cells are moved to reach the sorting device.
[0065] Preferably, the primary measuring device is arranged in a first solar cell testing device, and the further primary measuring device is arranged in a second solar cell testing device. In particular, the arrangement can be configured such that the primary measuring device and the further primary measuring device each receive a different group of solar cells for testing. If the solar cell testing system is integrated into a solar cell production plant or is arranged as an end-of-line cell tester at the end of a solar cell production plant that has two or more production lines, the first solar cell testing device can be set up at the end of a first production line, and the second solar cell testing device at the end of a second production line. In this case, the secondary measuring device serves both primary measuring devices.This has the advantage that each production line can be equipped with its own cost-effective and fast primary measuring device, while both production lines only need to have a common secondary measuring device, which can be correspondingly more expensive. According to a further aspect of the invention, a solar cell production plant is proposed. All configurations described above or below in connection with the solar cell production process can be implemented accordingly in the solar cell production plant.
[0066] The invention is explained below using exemplary embodiments with reference to the figures. Herein:
[0067] Fig. 1 shows a schematic representation of a solar cell testing system in the form of an end-of-line cell tester according to the prior art;
[0068] Fig. 2 shows a flowchart of a solar cell production process with a solar cell testing process according to a preferred embodiment;
[0069] Fig. 3 shows a schematic representation of a solar cell test system according to a preferred embodiment;
[0070] Fig. 4 shows a schematic representation of a solar cell test system according to a further preferred embodiment with a separate measuring path for the secondary measuring method;
[0071] Fig. 5 shows a schematic representation of a solar cell test system according to another preferred embodiment with several primary and secondary measuring devices;
[0072] Fig. 6 shows a schematic representation of a solar cell test system according to another preferred embodiment comprising solar cell buffers;
[0073] Fig. 7 shows a schematic representation of a solar cell test system according to another preferred embodiment, in which steps of the primary measurement method are carried out before completion of the solar cell; and
[0074] Fig. 8 shows a schematic representation of a solar cell testing system according to a preferred embodiment, which is designed to serve two solar cell production lines simultaneously. Fig. 1 schematically shows a solar cell testing system according to the prior art. It comprises a solar cell testing device 1 and a sorting device 40. All solar cells first pass through the solar cell testing device 1 and then reach the sorting device 40, where they are sorted into classification categories 41-44 according to the test results determined in the solar cell testing device 1. According to the prior art, each solar cell is subjected to a standard measuring procedure. This is illustrated in Fig. 1 by a standard measuring device 15, which the solar cells pass through in the solar cell testing device 1.Standard measuring device 15 is a tester for measuring solar cells under standard test conditions (STC). These are abbreviated to STC testers. The standard conditions (according to IEC 60904) include, in particular, standardized illumination / irradiation of the solar cell with a standard light spectrum (AM1.5G) and an illumination intensity of 1000 W / m. 2 and a solar cell temperature of 25°C. Deviating test conditions are corrected according to the standard. In addition, each solar cell is electrically contacted, and its current-voltage curve (IV curve) is measured during irradiation.
[0075] As an alternative to the situation shown in Fig. 1, two or more standard measuring devices 15 can be operated in parallel to increase throughput. Typically, the standard measuring devices 15 are arranged directly at the end of a production line, thus used for so-called end-of-line cell testing.
[0076] It should be noted here that the rectangles shown in the diagrams in Figures 1 and 3 to 8 can visualize both process steps within a process and corresponding device modules within a device. Thus, as explained above, Figure 1 can show a standard measuring device 15 to which all manufactured solar cells are fed, or standard measuring steps 15 or standard measuring methods 15 that are carried out in parallel on the manufactured solar cells. This dichotomy will be applied below without the need for explicit reference. In other words, the following explanations of the different embodiments of solar cell test systems can, where possible and reasonable, also be applied to embodiments of corresponding solar cell test methods.
[0077] After the standard measurement has been performed in the standard measuring device 15, the measurement results are passed on to an evaluation device 30. The evaluation device 30 evaluates the measurement results and determines one or more characteristic features for each solar cell, which then serve as the basis for classification into the corresponding classification category 41-44. For example, the measurement result of the standard measurement on a solar cell can consist of a measured UI characteristic curve, from which the evaluation device 30 then calculates a power value for the solar cell. The classification categories 41-44 can then be dimensioned such that, for example, the solar cells of the first classification category 41 can be used to produce a solar module of the 47 watt (W) module class, those of the second classification category 42 can be used to produce a solar module of the 51 W module class, etc. E.g.Depending on the color of the solar cell, there may be several subcategories per classification category 41-44.
[0078] Fig. 2 shows a flowchart of a solar cell production process according to an advantageous embodiment. In step 100, the production of a solar cell is summarized, which of course represents an extreme abbreviation of the actual situation. The subsequent steps 210 to 400 can also form a solar cell testing process according to a preferred embodiment separately, i.e., without the production step 100. For example, the solar cells can have been produced in a separate solar cell production facility and transported in groups to a solar cell testing facility. In the solar cell production process or solar cell testing process shown in Fig. 2, each produced solar cell is first subjected to a primary measurement method 210. The primary measurement result determined in the primary measurement method 210 is then evaluated using an evaluation method 300 to obtain an evaluation result.The evaluation method 300 is designed such that the evaluation result is positive (+) if the solar cell can be classified into a predetermined sorting category based exclusively on the primary measurement result, for example, if the primary measurement result already indicates that the solar cell has a certain performance, or if this can be derived from the primary measurement result. The evaluation result can, for example, also be positive (+) if the solar cell can be immediately classified as rejects, defective, or damaged based on the primary measurement result. The decision as to whether the evaluation result is positive (+) or negative (-) is shown in Fig. 2 as decision step 350. In a final step, if the evaluation result is positive, binning 400 takes place, in which the solar cell is classified accordingly.
[0079] Classification 400 may include steps by which the solar cell is placed in corresponding containers (bins), i.e., sorted into the containers. However, this is not mandatory. Rather, it is sufficient for classification 400 if an assignment is made between the solar cell and a respective classification category 41-44. For this purpose, for example, each solar cell can be provided with an identifier whose assignment to a classification category 41-44 is recorded electronically using an assignment list or table.
[0080] If, however, the evaluation result is negative (-), which is the case if the solar cell cannot be classified into a predetermined sorting category based solely on the primary measurement result, the solar cell is subjected to a secondary measurement method 220, in which a secondary measurement result is determined. The secondary measurement result will also preferably be evaluated in order to determine whether the solar cell belongs to a specific classification category 41-44. However, the goal of this evaluation is not to obtain an evaluation result as described above, because it is assumed that at least the secondary measurement result will serve as the basis for classification 400, as is customary in the prior art.
[0081] A solar cell testing system implementing the solar cell testing process is illustrated in the diagram in Fig. 3. A large number of solar cells are fed to the solar cell testing device 1, which is represented by a line from the left. All solar cells are first guided to a primary measuring device 10, in which the primary testing procedure takes place. The primary measurement results determined in this process are passed to an evaluation device 30, where they are evaluated. The evaluation result determines whether the primary measurement result determined for the respective solar cell is sufficient to classify the solar cell into predetermined sorting categories 41-44 on this basis. If this is not the case, the solar cell is tested again in a secondary measuring device 20 to obtain a secondary measurement result. From this secondary measurement result and, if applicable,The primary measurement result is then used to determine which classification category (41-44) the solar cell should be classified into. For example, the primary measuring device 10 can be an imaging, non-contact measuring device, such as a photoluminescence measuring device. In contrast, the secondary measuring device 20 can be designed for STC testing.
[0082] If the evaluation result is positive or if the secondary measurement result is available, the solar cell is sent to a classification device 40, where it is sorted according to a classification category 41-44. Fig. 3 shows four classification categories 41-44, although more or fewer classification categories can of course be provided. One possible categorization is according to the power class of the solar module in which the solar cells can be used. For example, a first classification category 41 can be assigned to a power class of 47 W, a second classification category 42 to a power class of 51 W, a third classification category 43 to a power class of 55 W, and a fourth classification category 44 to a power class of 59 W. Alternatively or additionally, classification categories for defective goods can also be provided.An alternative categorization can be defined such that each solar cell is classified according to its power output, e.g., under standard conditions. The four classification categories 41-44 can then be assigned to the solar cell power outputs 5.00W to 5.09W, 5.10W to 5.19W, 5.20W to 5.29W, and 5.30W to 5.39W, respectively. Of course, further classification categories can be provided in all cases.
[0083] In the solar cell testing system shown in Fig. 3, the secondary measuring device 20 is arranged such that all solar cells that have passed through the primary measuring device 10 will also pass through the secondary measuring device 20, since the primary measuring device 10 and the secondary measuring device 20 are located in the same measuring path (solid line) of the system. Here, the secondary measuring device 20 can be controlled so that only the desired solar cells are tested using the secondary measuring method. This has the disadvantage that during a long measurement using the secondary measuring method, the following solar cells have to wait for the measurement to be completed, which reduces throughput. An alternative arrangement is shown in Fig. 4. Here, the secondary measuring device 20 is located in a separate measuring path (dashed arrow).Only the solar cells that emerge from the primary measuring device 10 with a negative evaluation result are passed to the secondary measuring device 20 and tested there using the secondary measuring method. These solar cells, like those with a positive evaluation result, are then passed to the classification device 40 and sorted / classified there. While a single primary measuring device 10 and a single secondary measuring device 20 are shown in Figs. 3 and 4, in all embodiments the primary measuring device 10 can be designed to perform several different primary measuring methods on a solar cell simultaneously or sequentially. Likewise, in all embodiments the secondary measuring device 20 can be designed to perform several different secondary measuring methods on a solar cell simultaneously or sequentially, for example a measurement of an IV characteristic curve and a detection of a solar cell color.
[0084] In further embodiments, multiple primary measuring devices 10 and / or multiple secondary measuring devices 20 can be provided, which are arranged in different measuring paths. By way of example, Fig. 5 shows a solar cell testing device 1 according to an embodiment, which comprises the primary measuring device 10 and a further primary measuring device 11. Likewise, in addition to the secondary measuring device 20, four further secondary measuring devices 21-24 are provided, which perform the same secondary measurement or completely or partially different measurements on the solar cells. The evaluation device 30 collects the primary and secondary measurement results and distributes the solar cells, depending on the primary measurement results, to the secondary measuring devices 20-24 and subsequently to the classification categories 41-44 in the classification device 40.For example, if the primary measuring devices 10, 11 have different test speeds and / or the secondary measuring devices 20-24 have different test speeds, then the evaluation device 30 can be designed to increase or maximize the throughput of the solar cells through the solar cell testing device 1.
[0085] The solar cell testing process performed with the solar cell testing device 1 according to Fig. 5 can be described as the solar cells being subjected to a primary measurement method (corresponding to reference numeral 10) and subsequently to a further primary measurement method (11). Alternatively, however, it can also be stated that each solar cell is subjected to a primary measurement method composed of a first partial measurement (10) and a second partial measurement (11). Analogously, the secondary measurement method can be located in the secondary measuring device 20 and four further secondary measurement methods in the further secondary measuring devices 21-24, respectively, or the secondary measurement method can be viewed as being composed of five secondary partial measurements, each of which is performed in the secondary measuring device 20 and in the further secondary measuring devices 21-24.
[0086] In the embodiment according to Fig. 5, the solar cells are first measured in the primary measuring device 10 to obtain a primary measurement result, and then measured in the additional primary measuring device 11 to obtain another primary measurement result. If the primary measurement result already indicates that secondary measurement methods are necessary to correctly classify the solar cell, the solar cell is passed to the secondary measuring device 20 immediately after passing the primary measuring device 10. However, a solar cell can also be passed to the secondary measuring device 20 after passing the additional primary measuring device 11.Ultimately, the evaluation device 30 decides whether the solar cell to be measured using one of the several available secondary measuring methods 20-24 is fed to the secondary measuring device 20, fed to the first additional secondary measuring device 21, fed to the second additional secondary measuring device 23, and then routed to the third additional secondary measuring device 24 and finally to the first additional secondary measuring device 21. Finally, the evaluation device 30 can decide that the solar cell is routed to the fourth additional secondary measuring device 24 instead of to the secondary measuring device 20. The algorithm required for these decisions, which the evaluation device 30 uses, can preferably be self-learning. The solar cell test system shown in Fig. 6 differs from the embodiment shown in Fig. 5 by solar cell buffers 51, 52.A first solar cell buffer 51 is arranged upstream of the first additional secondary measuring device 21, while a second solar cell buffer 52 is arranged downstream of the first additional secondary measuring device 21. The solar cell buffers 51, 52 are designed to accommodate a plurality of solar cells in order to compensate for different / fluctuating throughputs within the different measuring paths. In the case illustrated in Fig. 6, the second solar cell buffer 52 is arranged at the end of a chain of three additional secondary measuring devices 21-23 and can, in particular, be designed to channel the solar cells accumulating in it between those solar cells that only pass through the primary measuring devices 10, 11 and are subsequently transported to the sorting device 40.
[0087] The solar cell testing system shown in Fig. 7 differs from the embodiment shown in Fig. 6 in that at least one additional primary measuring device 12 is arranged upstream of a production section 60. The production section 60 represents a production step, i.e., a step within the production line for manufacturing the solar cells. For example, the production step can be a temperature treatment, i.e., a tempering step. In this case, the production section 60 could be a furnace. Another additional primary measuring device 13 is arranged downstream of the production section 60 in the measurement path of the solar cells.
[0088] Finally, Fig. 8 shows a diagram of a solar cell testing system according to a preferred embodiment with two separate solar cell testing devices 1, 1'. The solar cell testing system is designed to serve as an end-of-line cell tester for two parallel production lines. While the part of the solar cell testing system intended exclusively for one production line reflects the solar cell testing system from Fig. 6, here all secondary measuring devices 20-24 and the associated solar cell buffers 51, 52 are outsourced to a separate distribution system 2. The solar cell testing device 1 for the first production line only contains the two primary measuring devices 10 and the evaluation device 30. The solar cell testing device 1' for the second production line contains the two further primary measuring devices 11 and a further evaluation device 30'.The secondary measuring devices 20-24 serve as common secondary measuring devices for both solar cell test devices 1, 1', and thus for both production lines. This arrangement has the advantage that a separate distribution system 2 with its own associated secondary measuring devices 20-24 can be eliminated for the second production line. This is possible because, during normal operation, only a fraction of the solar cells are subjected to the secondary measurement process.
[0089] Figs. 3 to 8 build on each other in that each subsequent figure contains all the features of the preceding figure and has been supplemented by a feature or concept, whereby Fig. 6 is more likely to be considered the predecessor of Fig. 8. However, it should be noted here that the concepts and features of the systems illustrated in Figs. 3 to 8 can also be combined independently of one another, as far as possible. For example, the buffers from Fig. 6 can be used in any other embodiment of Figs. 3 and 4.
[0090] List of reference symbols:
[0091] 1 solar cell test device
[0092] 1 ' additional solar cell test device
[0093] 2 Distribution system
[0094] 10 Primary measuring device
[0095] 11 additional primary measuring devices
[0096] 12, 13 additional primary measuring devices
[0097] 15 Standard measuring device
[0098] 20 Secondary measuring device
[0099] 21 first additional secondary measuring device
[0100] 22 second additional secondary measuring device
[0101] 23 third additional secondary measuring device
[0102] 24 fourth additional secondary measuring device
[0103] 30 Evaluation device
[0104] 30' additional evaluation device
[0105] 40 Classification device / Sorting device / Binning device
[0106] 41 first classification category
[0107] 42 second classification category
[0108] 43 third classification category
[0109] 44 fourth classification category
[0110] 40' additional classification device
[0111] 51 , 52 Solar cell buffer
[0112] 60 production sections
[0113] 100 solar cell production
[0114] 210 Primary measurement methods
[0115] 220 secondary measurement methods
[0116] 300 evaluation methods
[0117] 350 Evaluation result positive / negative
[0118] 400 Binning
Claims
Patent claims: 1 . A solar cell testing process for testing a plurality of solar cells at each end of one or more production lines, comprising performing the following steps on substantially each manufactured solar cell: - carrying out a primary measurement method (210) on the solar cell to determine a primary measurement result; - Evaluating the primary measurement result by means of an evaluation method (300) such that an evaluation result is determined, wherein the evaluation result is positive if it is determined by means of the evaluation result that the solar cell can be classified into a predetermined sorting category on the basis of the primary measurement result alone, and is negative if it is determined by means of the evaluation result that the solar cell cannot be classified into a predetermined sorting category on the basis of the primary measurement result alone; - Classifying (400) the solar cell into a sorting category depending on the primary measurement result if the evaluation result is positive, - Carrying out a secondary measurement method (220) on the solar cell to determine a secondary measurement result and classifying (400) the solar cell into a sorting category depending on the secondary measurement result and optionally the primary measurement result if the evaluation result is negative.
2. Solar cell testing process according to claim 1, characterized in that after carrying out the secondary measurement method (220) on the solar cell, the primary measurement method and / or the evaluation method are / is calibrated depending on the primary measurement result and the secondary measurement result.
3. Solar cell testing process according to claim 2, characterized in that the calibration of the primary measurement method and / or the The evaluation method comprises applying machine learning algorithms and / or an artificial neural network. The solar cell testing process according to one of the preceding claims, characterized in that the evaluation method comprises machine learning algorithms and / or comparisons of the primary measurement result with limit values. The solar cell testing process according to one of the preceding claims, characterized in that the primary measurement method comprises a contactless measurement method. The solar cell testing process according to one of the preceding claims, characterized in that the primary measurement method comprises an imaging measurement method and / or a non-imaging measurement method. The solar cell testing process according to one of the preceding claims, characterized in that the secondary measurement method comprises a contact measurement method.Solar cell testing process according to one of the preceding claims, characterized in that the primary measurement method or a partial measurement method of the primary measurement method is performed before a manufacturing step of the solar cell. Solar cell testing process according to one of the preceding claims, characterized in that the solar cell is held in a solar cell buffer before or after performing the secondary measurement method. Solar cell production process comprising manufacturing the plurality of solar cells and performing a solar cell testing process according to one of the preceding claims. Solar cell production process according to claim 10, characterized in that after performing the primary measurement method (210) or a partial measurement method of the primary measurement method on the solar cell, the solar cell is subjected to a process step for completing and / or modifying the solar cell, in particular a tempering step. A solar cell test system for testing a plurality of solar cells at the end of one or more production lines, comprising: - a primary measuring device for carrying out at least one primary measurement (110) by means of a primary measuring method on substantially each of the plurality of solar cells (11, 12) to determine a primary measurement result (115) for each of the plurality of solar cells (11, 12); - a secondary measuring device for performing a secondary measurement (120) by means of a secondary measuring method on at least one of the manufactured solar cells to determine a secondary measurement result (125); and - a sorting device (40) for classifying (150) each of the plurality of solar cells (11, 12) into a sorting category depending on the primary measurement result (115) and / or secondary measurement result (125) associated with the solar cell (11, 12), characterized in that the solar cell production system is designed to carry out the secondary measurement (120) by means of the secondary measurement method on a subset of the plurality of solar cells (11, 12) and to calibrate the primary measurement method and / or the primary measurement result (115) depending on the secondary measurement result (125). Solar cell testing system according to claim 12, characterized by solar cell buffers which are designed to hold a plurality or multiplicity of solar cells before they are supplied to the secondary measuring device and / or before they are fed to the sorting device (40) after the secondary measuring device. Solar cell testing system according to claim 12 or 13, characterized by a further primary measuring device (11) and a solar cell distribution system (2) which is designed to transport solar cells selectively from the primary measuring device (10) or from the further primary measuring device (11) to the secondary measuring device (20). Solar cell testing system according to claim 14, characterized in that the primary measuring device (10) is arranged in a first solar cell testing device (1) and the further primary measuring device (11) is arranged in a second solar cell testing device (1'), such that the primary measuring device (10) and the further primary measuring device (11) each receive a different group of solar cells for testing.Solar cell testing system according to one of claims 12 to 14, characterized in that the secondary measuring device (20) is arranged along a measuring path along which all solar cells are moved from the primary measuring device (1) to the sorting device (40), or in that the secondary measuring device (20) is arranged along a separate measuring path that deviates from a measuring path along which all solar cells are moved from the primary measuring device (1) to the sorting device (40). A solar cell production system comprising one or more production lines for manufacturing (100) a plurality of solar cells, and a solar cell testing system according to one of claims 12 to 16.
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WO2026142582A1