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    • 专利摘要:
    The invention relates to a method for testing the contacting quality of an electrical contact between a solar cell (1) and a contacting unit, comprising the following method steps: contacting the solar cell (1) with the contacting unit, wherein the contacting unit forms the solar cell at least with a plurality of contacting elements (4a, 4b) contacted electrically conductive. The invention is characterized in that in the contacted state luminescence radiation in the solar cell (1) is generated and a spatially resolved luminescence image of the solar cell (1) radiated luminescence is received and that by means of a contacting quality evaluation unit (8) a measure of the electrical Kontaktierungsgüte is calculated based on the intensity values of the luminescence image and / or derived therefrom variables.
    公开号:CH711709A2
    申请号:CH01486/16
    申请日:2016-11-09
    公开日:2017-05-15
    发明作者:Höfler Hannes；Rein Stefan；krieg Alexander；Ramspeck Klaus；Schenk Stefan
    申请人:Fraunhofer-Gesellschaft Zur Förderung Der Angewandten Forschung E V；Albert-Ludwigs-Universität Freiburg；H A L M Elektronik Gmbh；
    IPC主号:
    专利说明:

    Description: [0001] The invention relates to a method and a device for testing the contacting quality of an electrical contact between a solar cell and a contacting unit according to the preambles of claims 1 and 15.
    For the analysis and characterization of photovoltaic solar cells, a variety of measuring methods is known. In this case, an electrical contacting of the solar cell is often necessary. Typically, the contacting of the solar cell with a contacting unit, which comprises a plurality of contacting elements, such as spring-loaded Kontaktierungsstifte. Charge carriers are supplied to the solar cell via the contacting unit, charge carriers are discharged or voltage potentials are specified.
    The accuracy with which the desired measured variables are measured on a solar cell contacted in this way can depend essentially on the quality of the contacting. Faulty contacts, in which, for example, only a subset of the contacting elements forms an electrical contact and / or contacting elements, for example, due to incomplete mechanical contacts, have an increased contact resistance, can lead to measurement errors. Due to such measurement errors, for example, a faulty determination of the efficiency of the solar cell and consequently a faulty sorting into efficiency classes can take place.
    It is known to determine the Kontaktierungsgüte by ohmic resistances between contacting elements are measured, such as in the manual "Supplement: Grid resistance PVCTControl extension for the electrical examination of finger screen printing" J.Vollrath, h.a.l.m. elektronik GmbH, 60389 Frankfurt / M, Rev.2.0 / 20.09.2010.
    Disadvantages of this method are that often several contacting elements in this measurement electrically connected to each other, so are short-circuited, and only their common average Kontaktierungsgüte can be determined, so that, for example, the failure of a smaller subset of contacting elements can not be distinguished from a slight increase in the contact contact resistance of all contacting elements. Also, such a method can be used poorly when not connected to each other on the solar cell contacting elements, because due to the large number of required contacting a very large technical effort with the upper test of all these contacting elements would have to be operated, starting with the individual lead out of cables for a Variety of contacting elements, which can reach a number greater than 100 depending on the cell design.
    The present invention is therefore an object of the invention to provide an improved method and an improved device for testing the Kontaktierungsgüte an electrical contact between a solar cell and a contacting unit available, which avoids the aforementioned disadvantages.
    This object is achieved by a method according to claim 1, a device according to claim 15 and a use of luminescence radiation of a solar cell according to claim 16. Advantageous embodiments can be found in the dependent subclaims.
    The inventive method is preferably designed for implementation by means of the inventive device, in particular a preferred embodiment thereof. The device according to the invention is preferably designed for carrying out the method according to the invention, in particular a preferred embodiment thereof.
    The method according to the invention for testing the contacting quality of an electrical contact between a solar cell and a contacting unit comprises the following method steps: [0010] The solar cell is contacted with the contacting unit. In this case, the solar cell is contacted with at least a plurality of contacting elements of the contacting unit in an electrically conductive manner.
    It is essential that in the contacted state luminescence radiation is generated in the solar cell and a spatially resolved luminescence image of the radiated from the solar cell luminescence radiation is received. By means of a contacting quality evaluation unit, a measure of the electrical contacting quality is calculated on the basis of the intensity values of the luminescence image and / or variables derived therefrom.
    The present invention is based on the knowledge that by means of spatially resolved measurement of generated in the solar cell luminescence radiation in an apparatusally unaufwändiger way an automated assessment of Kontaktierungsgüte is possible. For this purpose, an evaluation of the intensity values of the luminescence radiation and / or variables derived therefrom can be used in a simple manner.
    The inventive method thus differs from the previously known, quoted above method for determining the Kontaktierungsgüte in particular by the fact that luminescence is used to assess the Kontaktierungsgüte.
    The spatially resolved measurement of luminescence radiation is already known for characterizing a solar cell and, for example, in Takashi Fuyuki et al., "Photograph surveying of minority carrier diffusion length in polycrystalline silicon solar cells by electroluminescence", APPLIED PHYSICS LETTERS 86, 262108, 2005, DOI: 10.1063 / 1.1978979.
    The inventive method differs from such prior art method in that the luminescence is used to assess the Kontaktierungsgüte and not for the characterization and analysis of properties of the solar cell itself.
    The inventive method has in particular the advantages that no explicit individual measurements of the contact resistance of the contacting elements are required. Furthermore, it is not necessary for assessing the quality of contacting that individual cables are routed out of all the contacting elements to form an evaluation unit.
    It is advantageous that the luminescence radiation is generated in the solar cell by means of power supply, at least partially via the contacting elements. This ensures that any inhomogeneities in the contacting quality are reflected in the distribution of the intensity values of the luminescence radiation. The luminescence radiation is therefore preferably so-called "electroluminescent radiation".
    Alternatively or additionally, luminescence radiation can be excited by an illumination of the solar cell and the spatially resolved measurement of the luminescence radiation can be carried out in a state in which charge carriers are removed via the contacting. The luminescence radiation may thus also be so-called "photoluminescence radiation".
    For the determination of the contacting quality, in particular the contrast of the luminescence image, i. E. the differences in the measured values of the luminescence image, relevant. In particular, it is not necessary to determine an absolute brightness level for each location point of the luminescence image.
    Advantageously, the luminescence image is normalized; in particular, a normalized luminescence image can be calculated by dividing the value of each individual measurement point by an average of all measured values.
    Based on the spatially resolved luminescence image can be deduced on the Kontaktierungsgüte. In an advantageous, particularly uncomplicated embodiment, a measure of the inhomogeneity of the measured values of the luminescence image is rated as a measure of the contacting quality: since inhomogeneous electrical contacts of the individual contacting elements lead to an inhomogeneous luminescence image, this mass can already be used as a measure of the electrical contacting quality , A simple measure for the inhomogeneity of the luminescence image can be formed in an advantageous embodiment by calculating the standard deviation of all intensity values of the luminescence image. A larger standard deviation thus indicates a more inhomogeneous luminescence image and thus a lower contacting quality compared to a luminescence image with a lower standard deviation.
    However, it is advantageous to use the information about the location of the contacting elements in the evaluation of the luminescence image, as described below: Advantageously, each of the contacting elements of the plurality of contacting elements is assigned a subset of pixels of the luminescence image and for each of these contacting elements In each case, the measure of the electrical contacting quality is calculated as a function of the respective assigned pixels of the luminescence image.
    In this way, an assignment of luminescence measured data to each of the plurality of contacting elements is thus effected in a simple manner in order to determine the contacting quality based thereon.
    Advantageously, there is a spatial segmentation of the luminescence image, wherein preferably a segmentation takes place in at least a number of segments, which corresponds to the number of the plurality of contacting elements. Each contacting element is assigned at least one segment according to the above-described division, preferably exactly one segment. For each contacting element, the measure of the electrical contacting quality is calculated as a function of the respectively assigned segment of the luminescence image.
    It is also possible to combine several contacting elements into groups and assign each group at least one segment, preferably exactly one segment. A group preferably comprises a plurality of adjacent contacting elements.
    The above-described segmentation thus makes it possible in a simple manner to take into account the spatial configuration of the contacting unit and thus in particular the spatial arrangement of the contacting elements in the assignment of the pixels of the luminescence image to the individual contacting elements.
    Advantageously, each contacting element is assigned a subset of pixels of the luminescence image which lie in an image region of the luminescence image surrounding the respective contacting element. This results in a spatial relationship between the pixels of the luminescence image and the associated contacting element.
    To check the Kontaktierungsgüte preferably each contact element is assigned a characteristic value which is determined depending on the subset of pixels of the luminescence image associated with the respective contacting element. This results in a simplification of the evaluation method to the effect that initially the predetermined by the number of pixels of the luminescence image amount of data, which is typically a multiple of the number of contacting elements, is reduced to a number of characteristics corresponding to the number of the plurality of contacting elements.
    Thus, for each contacting element, an individual characteristic value for this contacting element is preferably calculated as a function of the measured data of the assigned pixels. From the characteristic values of the plurality of contacting elements, a measure of the contacting quality is then calculated.
    In particular, it is advantageous in this case that the characteristic value is determined via an averaging method from measured values which belong to the subset of pixels assigned to the respective contacting element and the mass for the electrical contacting quality is calculated as a function of the respectively associated characteristic values.
    As a result, a characteristic value is assigned to the contacting elements in an inextricably manner without placing high demands on the computing capacity of the evaluation unit. In addition, robust, error-prone averaging methods are available, in particular arithmetic averaging.
    The averaging can in this case be carried out using known averaging methods, in particular as an alternative to said arithmetic averaging by other averaging methods.
    In particular, the use of a weighted averaging method is advantageous. In this case, in particular, a weighting is so advantageous that a measured value of the luminescence image is weighted with the distance to the associated contacting element, in particular in such a way that more distant measuring points have little influence compared to measured values of the luminescence image closer to the contacting element.
    A procedurally uncomplicated determination of a contacting quality is carried out in a preferred embodiment by specifying at least one threshold for classifying the Kontaktierungsgüte. In this case, each contacting element of the plurality of contacting elements is assigned a contacting quality class as a function of the relation of the characteristic value assigned to the contacting element to the threshold value.
    In this case, it is particularly advantageous to carry out normalization as described above.
    In a particularly simple embodiment, therefore, only one threshold value can be predetermined and each contacting element is assigned one of at least two, in particular exactly two, contacting quality classes, a first contacting quality class being assigned to those contacting elements whose characteristic value is greater than the threshold value and a second contacting quality class is assigned to the remaining contacting elements. An advantageous overall evaluation of the contacting quality can then take place via the number of contacting elements to which the second contacting quality class is assigned, wherein it should be noted that the spatial arrangement of the contacting elements, to which the second contacting quality class is assigned, preferably also flows into the overall evaluation. For example, two spatially adjacent contacting elements, to which the second contacting quality class is assigned, are to be regarded as more critical than two contacting elements located far apart from each other.
    As described above, in the method according to the invention, a measure of the contacting quality is calculated from the measured data of the luminescence image. In order to avoid errors, it is therefore advantageous that there is no change in the measuring arrangement between the contacting of the solar cell by means of the contacting unit and the recording of the luminescence image. In particular, it is advantageous not to change the arrangement of the contacting elements and preferably also other parameters, which have an effect on the electrical contact resistance, in particular a contact pressure of the contacting elements to the solar cell, not to change.
    By means of the method according to the invention, the contacting quality can be evaluated as described above. Preferably, therefore, at least one measurement is made in the contacted state for analysis and / or characterization of the solar cell. Such an analysis and characterization can already be done by the recorded luminescence image per se.
    In a preferred embodiment, therefore, the recorded luminescence image - if the Kontaktierungsgüte is classified as sufficient - used for the analysis and / or characterization of the solar cell.
    Alternatively or additionally, it is advantageous to perform at least one further measurement, in which an electrical contact is required to perform on the solar cell, in particular, without changing the electrical contact between receiving the luminescence image and the further measurement, in particular, without the arrangement to change the contacting elements and preferably without changing other parameters which affect the electrical contact resistance, in particular a contact pressure of the contacting elements to the solar cell.
    A typical analysis is carried out by measuring a current-voltage characteristic, which in particular allows the determination of a variety of global parameters of the solar cell. Preferably, therefore, a current-voltage characteristic of the solar cell is additionally measured in the contacted state of the solar cell. In this case, it is within the scope of the invention to measure the current-voltage characteristic without illumination (a so-called "dark characteristic") and / or the current-voltage characteristic with illumination, in particular with normalized illumination (a so-called "bright characteristic").
    The measure of the contacting quality can be calculated on the basis of a luminescence image. In an advantageous embodiment, a plurality of luminescence images of a single solar cell can be recorded. From the plurality of luminescence images, an evaluation luminescence image is calculated which forms the basis for evaluating the quality of the contacting.
    Advantageously, the recording conditions of the luminescence images differ to separate material-induced contrasts from contact-induced contrasts. In an advantageous embodiment, a plurality of luminescence images are recorded at different operating points of the solar cell. In particular, an evaluation luminescence image analogous to the description according to Markus Glatthaar et al., "Spatially resolved détermination of dark saturation current and sériés résistance of Silicon solar cells", Phys. Status Solidi RRL4, no. 1.13-15 (2010) / DO110.1002 / pssr.200903290.
    In a further advantageous embodiment of the method according to the invention, luminescence images of at least two, different solar cells are used to evaluate the contacting quality. In this way, defect influences based on cell defects in the solar cells can be avoided or at least reduced: Preferably, in addition to the luminescence image, at least one further, second luminescence image of at least one further, second solar cell is measured as the first luminescence image of a first solar cell. From the at least two luminescence images, a common evaluation luminescence image is calculated. By means of the contacting quality evaluation unit, the measure of the electrical contacting quality is calculated for each contacting element of the plurality of contacting elements as a function of the data of the evaluation luminescence image.
    This results in the advantage that a cell defect which leads to an inhomogeneity in the intensity values of the luminescence image, does not or only slightly affects the overall evaluation, since with high probability the second solar cell no such cell defect or at least not at the same Location and thus due to the calculation of a common evaluation luminescence image, the influence of such cell defects is reduced.
    The calculation of the common evaluation luminescence image is preferably carried out with an averaging process. In particular, it is within the scope of the invention to add for each pixel in each case the intensity values or values resulting therefrom and then to normalize them, in particular in which the number of accumulated luminescence images divides them.
    In this case, it is particularly advantageous to carry out a continuous correction of the evaluation luminescence image: In this advantageous embodiment, a luminescence image is successively recorded for a large number of solar cells. As described above, an evaluation luminescence image is calculated from the first two luminescence images, particularly preferably by averaging. Subsequently, the evaluation luminescence image is corrected by means of the luminescence image of the third solar cell, i. H. Preferably, a further averaging is carried out on the basis of the third luminescence image, preferably with a weighting, so that in the present case the data of the evaluation luminescent image averaged out of two Luminescence zenz images is weighted by a factor of 2 and the data of the third luminescence image only by a factor of 1 in the averaging process ,
    In a further advantageous embodiment, an averaging is first carried out as described above for a predetermined number N of solar cells. Averaging is then carried out for each additional image by weighting the previously calculated evaluation luminescence image with a factor (N-1) / N and correspondingly the current luminescence image with a factor of 1 / N.
    If threshold values are predetermined for assessing the quality of contacting, as described above, it is advantageous to predefine the threshold values as a function of the number N of luminescence images by means of which the evaluation luminescence image is calculated. In this case, it is particularly advantageous to design the threshold values with a smaller number N of the luminescence images used in such a way that larger deviations are tolerated, compared with the threshold values for a large number N of luminescence images.
    In an advantageous embodiment, a threshold value S1 is predetermined for a number N = 1 and a threshold value Su for a number N = infinite. The dependence of the threshold value of N can then be determined, for example, via the functional specification S (N) = - (Su-S1) * exp (-a * (N-1)) + Su, where a is a parameter to be determined. Such a function converges to the value Su for large values of N. An exemplary parameter set, which however is to be determined individually for each solar cell type, is S1 = 0.7, Su = 0.9 and a = 0.05.
    Such a method is particularly advantageous in process monitoring processes during the production of solar cells, in which continuous or quasi-continuous monitoring of the solar cells produced is to take place. In this case, it is particularly advantageous to predefine a number N of solar cells, by means of whose luminescence images the evaluation luminescence image is calculated in each case. It is thus particularly advantageous to calculate the evaluation luminescence image by averaging the last N luminescence images, where N is preferably in the range from 100 to 10,000.
    It is within the scope of the invention to measure each solar cell or merely a random selection, for example, to measure only every n-th solar cell, for example, every second or every third solar cell in the manufacturing process.
    Additionally or alternatively, it is advantageous that the measured luminescence image is cleaned up, with a pattern recognition algorithm measuring data, which are caused by cell defects, corrected or eliminated. In this advantageous embodiment, the mass for the electrical contacting quality is thus calculated for each contacting element as a function of the data of the corrected luminescence image.
    Prominent cell defects which cause contrasts in luminescent images are, for example: local interruptions of the front-side contacting structure (finger breaks), poorly formed metal-semiconductor contacts, process-related locally increased recombination activity, cracking, material inhomogeneities in multicrystalline base material.
    All listed cell defects leave characteristic patterns in luminescence images. Local finger interruptions leave easily detectable image signatures. Algorithms for detecting finger breaks are already commercially available. Poorly formed metal-semiconductor contacts leave characteristic patterns depending on the contact formation process. For example, chain-belt structures which are an image of the conveyor belt of the high-temperature furnace in which the metal-semiconductor contact formation takes place are a frequently occurring contrast phenomenon that can be detected via a pattern recognition algorithm. Process-related locally increased recombination activity can be induced, for example, by impurities driven in by conveyor belts. These typically leave streaks in the characteristic distances of the conveyor belts. Furthermore, support positions of the solar cells in process machines are often visible in luminescence images. Since these are in known locations and at the same time have characteristic contrasts, the contrasts can be identified particularly easily by a pattern recognition algorithm. The automatic detection of material inhomogeneities and cracks is described for example in WO 2012/172 073.
    Advantageously, a correction of a luminescence image is carried out in such a way that at the location of the localized cell defect, the intensity of the surrounding measuring sites, which is not increased or decreased by the localized cell defect, is adjusted due to the cell defect, for example by an average of the measured values not being adjusted is created by the localized cell defect influenced, surrounding measuring sites and the measured values are set at the locations of the cell defect on this average.
    Again, there is thus the advantage that no or at least lower errors in the determination of the electrical Kontaktierungsgüte caused by cell defects.
    In addition, it is advantageous to simulate voltage distributions on the solar cell via a model representing the respective solar cell structure, as described, for example, in S. Eidelloth et al., "Simulation tool for equivalent circuit modeling of photovoltaic decices", IEEE Journal of Photovoltaics, Vol. 2, 2012, and to derive a simulated luminescence image from the simulated voltage distributions in a manner known per se. Advantageously, for a given solar cell design, a set of luminescent images is simulated, each of which represents a particular array of "good" and / or "bad" contacting contacting elements. The evaluation of the contacting quality of the contacted solar cell is then made by comparing the measured luminescence image with the set of simulated luminescence images such that the image from the set of simulated luminescence images which is most similar to the measured luminescence image is assigned to the measured luminescence image.
    In addition to cell defects, which are based on inhomogeneous electronic semiconductor properties or inhomogeneous optical properties, in particular defects in metallic contacting structures of the solar cell are an impairment in determining the Kontaktierungsgüte. Advantageously, therefore, additionally an optical image of contacting structures of the solar cell, which by means of Contacting be contacted electrically, added. Damage and / or interruptions of the contacting structures are localized on the basis of the optical image.
    In this case, the measured luminescence image is preferably adjusted as a function of the optical image, in particular the localized damage and / or interruptions of the contacting structures. In this case, measurement data lying in the region of the localized damage and / or interruptions are preferably corrected or eliminated. Accordingly, the measure of the electrical contacting quality is calculated as a function of the data of the corrected luminescence image for each contacting element.
    As already described above, the electrical contacting of the solar cell can be used in particular for measuring a current-voltage characteristic of the solar cell. From such a current-voltage characteristic characteristic data can be calculated in a conventional manner, which also allow a conclusion on the Kontaktierungsgüte. Such characteristics are in particular a global series resistance Rs, which can be extracted from the characteristic curves according to IEC 60 891 and / or the fill factor of the solar cell.
    Preferably, a measure of the contacting quality is calculated from a combination of characteristic values which are calculated from the luminescence image measured under the contacting and characteristic values which are extracted from the current-voltage characteristic curve.
    A further possibility of a supplementary measurement to support the evaluation of the contacting quality is the measurement of electrical resistances between at least two contacting elements in the contacted state: In the contacted state, the contacting elements are at least partially electrically conductively connected to one another via the solar cell. This concerns in particular such contacting elements, which have a common metallic
    Contact the contacting structure of the solar cell. A measurement of the electrical resistance between at least two contacting elements thus also gives an indication of the contacting quality.
    Advantageously, therefore, the measure of the contacting quality is calculated as a function of a combination of values and values following from the intensity values of the luminescence image, which values are calculated from a measurement of an electrical resistance between at least two contacting elements in the contacted state.
    The evaluation of the Kontaktierungsgüte exclusively due to the measurement of the electrical resistance between at least two contacting elements - as mentioned in the introduction - known per se. A combination of this method with the previously described evaluation of the data of the luminescence image significantly reduces the susceptibility to errors in the evaluation of the electrical contacting quality.
    The method according to the invention is particularly suitable for testing the contacting quality, wherein the contacting unit electrically contacts the solar cell in that the plurality of contacting elements electrically conductively contacts a metallic contacting structure of the solar cell at a plurality of location points. Such contacts of solar cells are known per se. In particular, the use of so-called measuring strips is known as a contacting unit. Such measuring strips typically have a plurality of contacting elements arranged approximately in a linear manner, in particular in a straight line. Such contacting elements are preferably designed as spring-loaded Kontaktierungsstifte.
    Furthermore, it is known to provide in each case a pairwise arrangement of two contacting elements in the contacting unit. Here, a first group of contacting elements for impressing a voltage and supplying or discharging current is provided and a second group of contacting elements for measuring the resulting voltage of the solar cell. A pre-described pair of contacting elements typically includes a voltage measuring and a current-carrying contacting element.
    The method according to the invention, which uses contrast information from EL images, only allows conclusions about the contacting quality of the current-carrying or voltage-impressing group of contacting elements in the above-described configuration. It does not allow conclusions about the contact quality of the voltage-measuring group of contacting elements. By measuring the resistance between a current-carrying and a voltage-measuring group, additional conclusions can be drawn about the contacting quality of the voltage-measuring group. Such an advantageous embodiment of the inventive method thus allows conclusions about both groups of contacting elements.
    The above-mentioned object is further achieved by a device for testing the contacting quality of the electrical contact between a solar cell and a contacting unit according to claim 15. The device according to the invention has a contacting unit which has a plurality of contacting elements. The contacting elements serve for electrically contacting the solar cell.
    It is essential that the device has a camera for the spatially resolved measurement of luminescence radiation and a contacting quality evaluation unit. The contacting quality evaluation unit is designed to calculate a measure of the electrical contacting quality based on intensity values of the luminescence image of a luminescence image recorded by the camera and / or variables derived therefrom.
    The device according to the invention thus makes it possible to carry out the method according to the invention, so that the contacting quality can be evaluated by evaluating the luminescence image. In prior art devices which have a camera for receiving luminescence radiation, the luminescence radiation was used exclusively for analyzing the solar cell.
    The contacting unit can - as described above - be formed in a conventional manner. In particular, the contacting unit preferably has one or more contacting strips. The contacting elements are preferably designed as individual contacting pins, particularly preferably as spring-loaded contacting pins. However, other forms of contacting unit can also be used, in particular those which are designed to contact cells which have no current bus bars on the front, so-called busless solar cells, as well as cells which are contacted exclusively via the rear side.
    Depending on the cell design, solar cells have differently arranged metallic contacting structures on the side which faces and / or faces away from the incidence of light. The contacting unit is therefore preferably adapted to the respective geometry of the contacting structure of the respective solar cell, wherein the contacting unit is preferably designed such that it does not shade either incident light or light emitted by the solar cell. Furthermore, the contacting unit is preferably designed such that the contacting elements of the contacting unit are arranged in such a way that loss-free or at least approximately loss-free current discharge from the solar cell is made possible with sufficient contacting quality.
    Typical metallic contacting structures of a solar cell have a plurality of line-like metallization fingers. In particular, an embodiment of Kontaktierungsgittern having comb-like or double-comb-like structures is known. The contacting unit is therefore preferably designed such that in the contacted state, the contacting unit does not cover areas of the solar cell, or only slightly beyond the metallic front-side contacting. This ensures that, if necessary, exposure of the solar cell to radiation during the measurement is not or only slightly affected by shading by the contacting unit. Likewise, luminescence radiation generated in the solar cell is not or only slightly shadowed by the contacting unit.
    The camera is preferably arranged on contacted solar cell over the solar cell to record a spatially resolved luminescence image in a simple manner and with low optical distortion can. The camera is preferably designed in such a way that, as in a known manner, it receives only or only largely light in the spectral range of the emitted luminescent light. This can preferably be achieved by the use of optical filters in the beam path between the cell and the camera.
    Further preferred features and embodiments are explained below with reference to exemplary embodiments and the figures. Showing:
    1 shows a first embodiment of an inventive device.
    FIG. 2 shows a contact strip of a contacting unit of the device according to FIG. 1 and FIG
    Fig. 3 is a plan view from above of a contacted by means of the device according to FIG. 1 solar cell and
    Fig. 4 shows a second embodiment of an inventive device.
    In the figures, like reference numerals designate like or equivalent elements.
    In Fig. 1, a first embodiment of an inventive device for testing the Kontaktierungsgüte the electrical contact of a solar cell 1 is shown. The device has a contacting unit for electrically contacting the solar cell, which in the present case has two contact strips 2a and 2b, but depending on the solar cell design, may also have a plurality of contact strips, of which FIG. 1 shows a first contact strip 2a in a side view.
    The contact strips 2a and 2b are used for front side contacting of the solar cell 1. The contacting further comprises a back side contacting unit, which is presently designed as a measuring block 3, but depending on the solar cell design in the form of contact strips or otherwise formed. The measuring block 3 is used to place the solar cell 1 and to form an electrical contact with a metallic rear side contact of the solar cell 1, in this case with a full-surface, metallic rear contact.
    In the present case, the measuring block 3 has a supporting surface for the back side of the solar cell 1, which is penetrated at a plurality of openings by contacting elements of the rear-side contacting unit in order to form an electrical contact with the back side of the solar cell.
    As can be seen in FIG. 2, which shows a side view of the identically formed contact strips 2 a and 2 b, contacting elements 2 a and 2 b are arranged in pairs on the contact strips. These serve in the present embodiment in a conventional manner, on the one hand for measuring a voltage and on the other hand, for the supply or removal of charge carriers. In the present case, a pair of contacting elements thus comprises in each case a so-called current-carrying and a so-called voltage-measuring contacting element. By way of example, a pair is designated by a contacting element 4a and a contacting element 4b. The contacting elements are presently each formed as a spring-loaded Kontaktierungsstifte.
    By means of the contact strips 2a and 2b, rectangular metallic contacting structures on the front side of the solar cell 1, so-called busbars, are contacted in an electrically conductive manner: FIG. 3 shows a top view of the solar cell 1 from above Solar cell present on the front of a known, grid-like metallic contacting structure. This comprises two busbars 5a and 5b, which extend parallel to each other. Perpendicular to the busbars 5a and 5b extend a plurality of metallic Kontaktierungsfinger, of which two Kontaktierungsfinger 6a and 6b are characterized by way of example.
    The first contact strip 2a is arranged in the contacted state of the solar cell along the line A-A, so that the contacting elements 4a and 4b electrically contact the busbar 5a. Accordingly, the second contact strip 2b is arranged along the line B-B in order to electrically contact the second busbar 5b by means of the contacting elements of the second contact strip 2b.
    It is essential that the device according to FIG. 1 furthermore has a camera 7 for the spatially resolved measurement of luminescence radiation which is generated in the solar cell 1. Furthermore, the device has a Kontak-Tierungsgüteauswerteeinheit. The contacting quality evaluation unit is designed to calculate a measure of the electrical contacting quality based on intensity values of the luminescence image of a luminescence image recorded by the camera 7 and / or variables derived therefrom.
    In the present case, the contacting-quality unit is structurally combined with other components, in particular a controllable current-voltage source and measuring units for measuring characteristic curves in a measuring / evaluation unit 8.
    For this purpose, the measuring value unit 8 is connected to the camera 7, to the contact strips 2a and 2b and thus to all the contacting elements, as well as to the rear-side contacting unit and thus in particular to all the contacting elements of the measuring block 3.
    In a first exemplary embodiment of a method according to the invention, the solar cell 1 is contacted with the contacting unit, so that the front side of the solar cell is electrically contacted by means of the contact strips 2a and 2b and the rear side by means of the measuring block 3 as described above. By supplying current by means of the measuring / evaluation unit 8, luminescence radiation is generated in the solar cell 1, which is thus what is known as electroluminescent radiation.
    By means of the camera 7, a spatially resolved image of the luminescence radiation is recorded. Due to the arrangement of the contact strips 2a and 2b along the busbars 5a and 5b, there is thus no or only negligible impairment of the recorded luminescence image due to the contact strips located in the beam path between the solar cell and the camera 7.
    By means of the measuring / evaluation unit 8, a measure of the electrical contacting quality is calculated as a function of intensity values of the luminescence image: In the present exemplary embodiment, a spatial segmentation of the luminescence image takes place according to the division shown in dashed lines in FIG are exemplified by points on the busbars the contacting locations at which the busbars are contacted by contacting elements of the contact strips electrically. For better representability, the number of contact points has been reduced compared to typical numbers; Likewise, the pairs of contacting elements were each combined into a contact point. Common numbers of contact points as well as distances depend strongly on the design of the respective solar cells to be measured. For example, a common design has 3 contact strips spaced 52 mm apart and 11 pairs of contact elements per contact strip spaced about 14.2 mm apart.
    Each pair of contacting elements is assigned a segment of the spatial segmentation, wherein the contacting point is located approximately in the center of the respectively assigned spatial segment. Each pair of contacting elements is thus associated with a subset of pixels of the luminescence image, which belong to pixels of the respective associated segment.
    For each segment, an average value is calculated from the assigned pixels of the luminescence image, in this case an arithmetic mean value, so that an (averaged) intensity value (a characteristic value) is assigned to each pair of contacting elements based on the measured luminescence image.
    These characteristic values represent a measure of the contacting quality of the electrical contacting of the solar cell by the respective pair of contacting elements.
    In an advantageous development of the first exemplary embodiment, a threshold value is additionally predefined, so that two classes can be formed: A first class is assigned to pairs of contacting elements whose mean value determined as described above is less than or equal to the predetermined threshold value. A second class is assigned the remaining pairs of contacting elements. In particular, a threshold value dependent on the mean intensity value of the image of the total cell can be selected here, which is therefore calculated for each cell in a self-consistent manner from the present electroluminescent image.
    The 2 × 4 characteristic values obtained according to the present example are divided by the mean value of all the characteristic values, so that the characteristic values thus obtained assume numerical values which fluctuate around 1. It was thus a normalization.
    It is then defined from pre-experiments or empirical values a number enclosing the number 1. In the present example, a contacting element is assigned to a first contacting quality class if the characteristic value assigned to the contacting element is outside the defined interval. All contacting elements whose characteristic values lie within the interval are assigned to a second contacting quality class.
    Such a preliminary experiment can be a series of measurements in which faulty contacts of contacting elements are artificially brought about and the limits of the aforementioned interval are determined via the characteristic values occurring in this case.
    In order to avoid distortions, both the arrangement of the contacting elements on the busbars, and a contact pressure, by means of which the spring-loaded contact pins are pressed onto the busbars, between the contact of the solar cell and measuring the luminescence image is not changed.
    If a sufficiently high contact quality is determined as a result of the above-described automated quality evaluation, then a current-voltage characteristic of the solar cell 1 is recorded in a further advantageous development of the method, wherein this measurement is carried out by means of the measurement value unit 8 in a manner known per se becomes. It is also possible to evaluate an already recorded current-voltage curve on the basis of the determined Kontaktierungsgüte subsequently or even discard.
    权利要求:
    Claims (16)
    [1]
    1. A method for testing the contacting quality of an electrical contact between a solar cell (1) and a contacting unit, comprising the following method steps: contacting the solar cell with the contacting unit, wherein the contacting unit electrically contacts the solar cell (1) with at least a plurality of contacting elements in that in the contacted state luminescence radiation is generated in the solar cell (1) and a spatially resolved luminescence image of the solar cell (1) emitted luminescence is received and that by means of a contacting quality evaluation unit (8,8 ') a measure of the electrical Kontaktierungsgüte based is calculated on the intensity values of the luminescence image and / or variables derived therefrom.
    [2]
    2. The method according to claim 1, characterized in that each contacting element (4a, 4b) of the plurality of contacting elements is assigned a subset of pixels of the luminescence image and for each contacting element (4a, 4b) the measure of the electrical Kontaktierungsgüte depending on the respectively associated Pixels of the luminescence image is calculated.
    [3]
    3. The method according to claim 2, characterized in that a spatial segmentation of the luminescence image is carried out, preferably in at least a number of segments, which corresponds to the number of contacting elements, that each contacting element (4a, 4b) of the plurality of contacting elements at least one segment, Preferably, exactly one segment is assigned and for each contacting element (4a, 4b), the mass for the electrical contacting quality is calculated as a function of the respectively assigned segment of the luminescence image.
    [4]
    4. The method according to any one of claims 2 to 3, characterized in that each contacting element (4a, 4b) of the plurality of contacting elements, a subset of pixels is assigned, which are in a respective contacting element (4a, 4b) surrounding image area of the luminescence image.
    [5]
    5. The method according to any one of claims 2 to 4, characterized in that each contacting element (4a, 4b) of the plurality of contacting elements a characteristic value is assigned, which is determined depending on the respective contacting element (4a, 4b) associated subset of pixels, in particular, that the characteristic value is determined via an averaging method from measured values which belong to the subset of pixels assigned to the respective contacting element (4a, 4b) and the mass for the electrical contacting quality is calculated as a function of the respectively assigned characteristic values.
    [6]
    6. The method according to claim 5, characterized in that at least one threshold value for the classification of the Kontaktierungsgüte is given and each Kontaktierungselement (4a, 4b) is assigned a Kontaktierungsgüteklasse depending on the relation of the contacting element (4a, 4b) associated characteristic value to the threshold value, in particular, that each contacting element (4a, 4b) is assigned exactly one threshold value and each contacting element (4a, 4b) is assigned one of at least two contacting quality classes as a function of the relation of the contacting element (4a, 4b) associated characteristic value to the threshold value.
    [7]
    7. The method according to any one of the preceding claims, characterized in that the luminescence radiation is generated in the solar cell (1) by means of power supply at least partially via the contacting elements.
    [8]
    8. The method according to any one of the preceding claims, characterized in that between the contacting of the solar cell (1) and the recording of the luminescence image, the arrangement of the contacting elements is not changed.
    [9]
    9. The method according to any one of the preceding claims, characterized in that in addition to the luminescence image as the first luminescence image of a first solar cell (1) at least one further, second luminescence image of at least one further, second solar cell (1) is measured, and that a common evaluation luminescence from the measurement data of the first and at least the second Lumineszenzbildes is calculated, preferably by means of an averaging method, and that by means of the Kontaktierungsgüteauswer- teeinheit (8, 8) for each contacting element (4a, 4b) of the plurality of contacting elements, the measure of the electrical Kontaktierungsgüte is calculated from the data of the evaluation luminescence image, in particular that for at least one further solar cell (1), preferably for a plurality of further solar cells, a luminescence image is taken and the evaluation luminescence image is corrected by means of the measured data of the luminescence image.
    [10]
    10. The method according to any one of the preceding claims, characterized in that the measured luminescence image is cleaned, with a pattern recognition algorithm measurement data, which are caused by cell defects, corrected or eliminated and for each contacting element (4a, 4b) the measure of the electrical Kontaktierungsgüte is calculated depending on the data of the corrected luminescence image.
    [11]
    11. The method according to any one of the preceding claims, characterized in that a simulation of the voltage distribution in the solar cell (1), which prevail during the measurement of the luminescence image is performed, and a resulting, simulated luminescence image is derived and that by comparing the simulated and of the measured luminescence image, the measure for the electrical contacting quality is calculated, in particular that a measure of the contacting quality between contacting element (4a, 4b) and solar cell (1) is determined by comparing the simulated and the measured luminescence image for each contacting element (4a, 4b) , in particular by means of an iterative method.
    [12]
    12. The method according to any one of the preceding claims, characterized in that additionally an optical image of contacting structures of the solar cell (1), which are electrically contacted by the contacting unit, is recorded and located on the basis of the optical image damage and / or interruptions of the contacting structures, Preferably, that the measured luminescence image is adjusted depending on the optical image, wherein measured data, which are in the range of localized damage and / or interruptions, corrected or eliminated and for each contacting element (4a, 4b) the measure of the electrical Kontaktierungsgüte depending on the data of the corrected luminescence image is calculated.
    [13]
    13. The method according to any one of the preceding claims, characterized in that in the contacted state, in addition, a current-voltage characteristic of the solar cell (1) is measured, in particular, that a measure of the Kontaktierungsgüte from a combination of characteristics, from the under Contacting measured luminescence image are calculated, and characteristics that are extracted from the current-voltage characteristic is calculated.
    [14]
    14. The method according to any one of the preceding claims, characterized in that the measure of the Kontaktierungsgüte is calculated in dependence on the following from the intensity values of the luminescence image values and values calculated from the measurement of an electrical resistance between at least two contacting elements in the contacted state become.
    [15]
    15. A device for testing the contacting quality of the electrical contact between a solar cell (1) and a contacting unit, comprising a contacting unit, which has a plurality of contacting elements for electrically contacting the solar cell (1), characterized in that the device comprises a camera (7). for the spatially resolved measurement of luminescence radiation and a contacting quality evaluation unit (8, 8 ') and in that the contacting quality evaluation unit (8, 8 ") is designed to provide a measure of the electrical contacting quality based on intensity values of the luminescence image of at least one of Camera (7) recorded luminescence image and / or derived therefrom variables.
    [16]
    16. Use of luminescence radiation of a solar cell (1), which is electrically contacted with a contacting unit having a plurality of contacting elements, for calculating a measure of the electrical contacting quality between the contacting unit and the solar cell (1).
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    同族专利:
    公开号 | 公开日
    DE102015119360A1|2017-05-11|
    CH711709B1|2017-08-15|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    DE102011105182A1|2011-06-17|2012-12-20|Albert-Ludwigs-Universität Freiburg|A method of providing a predictive model for crack detection and a method of crack detection on a semiconductor structure|
    DE102011081004A1|2011-08-16|2013-02-21|Solarworld Innovations Gmbh|Contact device for solar cell with flexible line-shaped contact element, has carrier, and two parallel running linear electrically conductive contact strips or contact paths that are attached on carrier|DE102020117760A1|2020-07-06|2022-01-13|Wavelabs Solar Metrology Systems Gmbh|Contacting device, solar cell test device and light source|
    法律状态:
    2020-09-30| PFA| Name/firm changed|Owner name: ALBERT-LUDWIGS-UNIVERSITAET FREIBURG, DE Free format text: FORMER OWNER: ALBERT-LUDWIGS-UNIVERSITAET FREIBURG, DE |
    优先权:
    申请号 | 申请日 | 专利标题
    DE102015119360.4A|DE102015119360A1|2015-11-10|2015-11-10|Method and device for testing the contacting quality of an electrical contact between a solar cell and a contacting unit|
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