METHOD AND DEVICE FOR THE ANALYSIS OF A MULTI-SOLAR CELL WITH AT LEAST TWO SUB-SOLAR CELLS USING LUMINESCENT RADIATION

Description

[0001] In the case of doped semiconductor substrates, particularly silicon wafers and devices based on them such as photovoltaic solar cells, it is known to obtain information about the material parameters of the semiconductor substrate or the properties of the device by measuring the luminescence radiation generated in the semiconductor. Such a device is described in WO 2007 / 041758 A1 and in EP 1 840 541 A1.

[0002] Furthermore, luminescence analysis offers the advantage that semiconductor devices with multiple pn junctions can also be analyzed. For example, multi-junction solar cells are known to increase efficiency. In these cells, several pn junctions are arranged one above the other in a layered structure, so that several sub-solar cells are stacked on top of each other, starting from a surface of the solar cell facing the incident radiation. These sub-solar cells are optimized for converting different spectral components of the incident radiation. Typically, the uppermost sub-solar cells are optimized for shorter wavelength spectral ranges, and the lowermost sub-solar cells are optimized for longer wavelength spectral ranges, which have a greater penetration depth.

[0003] Multi-junction solar cells can also be analyzed using luminescence radiation. In typical multi-junction solar cells, the various sub-junctions emit luminescence radiation in different wavelength ranges, allowing for the separation of the emitted luminescence radiation and thus enabling separate analyses of the individual sub-junctions. This involves spatially resolved detection of the emitted luminescence radiation, allowing for a spatially resolved analysis of each sub-junction.

[0004] Such a use of luminescence radiation for the analysis of a multi-junction solar cell with two sub-junctions (a tandem solar cell) is described in IEEE JOURNAL OF PHOTOVOLTAICS, VOL. 7, NO. 4, JULY 2017, p. 108, "Nondestructive Probing of Perovskite Silicon Tandem Solar Cells Using Multiwavelength Photoluminescence Mapping," by Laura E. Mundt et al. This method employs two different luminescence detectors, each designed to detect luminescence radiation in different wavelength ranges. A first detector is used to analyze the first sub-junction, and a second detector is used to analyze the second sub-junction. Further methods for measuring multi-junction solar cells are known from EP 2 378 278 A1 and FR 3 038 165.

[0005] With the increasing transfer of manufacturing processes for multi-junction solar cells from laboratory scale to industrial production, there is a need to analyze multi-junction solar cells cost-effectively.

[0006] The present invention therefore aims to provide a method and a device for analyzing a multi-junction solar cell with at least two sub-solar cells using luminescence radiation, which are error-free and cost-effective.

[0007] This problem is solved by a method according to claim 1 and a device according to claim 7. Advantageous embodiments are found in the dependent subclaims.

[0008] The method according to the invention is preferably designed to be carried out using the device according to the invention, in particular an advantageous embodiment thereof. The device according to the invention is preferably designed to carry out the method according to the invention, in particular a preferred embodiment thereof.

[0009] The inventive method for analyzing a multi-junction solar cell with at least two sub-junction solar cells using luminescence radiation comprises a process step A in which luminescence radiation is generated in the sub-junction solar cells by subjecting the multi-junction solar cell to excitation radiation and / or applying an electrical voltage to contacts of the multi-junction solar cell. Luminescence radiation is thus generated in the sub-junction solar cells in a manner known per se, for carrying out a so-called electroluminescence method and / or photoluminescence method.

[0010] In process step B, the luminescence radiation is detected with spatial resolution using at least one multi-element detector with a plurality of detector elements, and different spectral ranges of the luminescence radiation for the different sub-solar cells are evaluated.

[0011] It is therefore possible to perform a separate analysis of the individual sub-solar cells based on the evaluation of the different spectral ranges of the luminescence radiation, whereby each sub-solar cell can be analyzed with spatial resolution.

[0012] Essentially, in process step B, the detector elements are simultaneously exposed to luminescence radiation emitted by the multi-junction solar cell. A first group of detector elements captures a first spectral range, while at least a second group of detector elements, distinct from the first, captures at least a second spectral range. The first and second spectral ranges, and optionally any further spectral ranges, are different, and the spectral sensitivities of the different groups of detector elements exhibit different spectral centers. The intensity of the luminescence radiation is attenuated or completely blocked in an overlapping spectral range where the sensitivities of the at least two groups of detector elements overlap.

[0013] The method according to the invention thus provides, when using a multi-element detector, for a subdivision of the detector elements of the multi-element detector into at least two groups, which are assigned to different spectral ranges.

[0014] This eliminates the need for multiple separate detectors for different spectral ranges and the mechanical exchange of these detectors or the mechanical replacement of optical filters for detecting different spectral ranges. The method can therefore be implemented with a device that has fewer and / or fewer moving parts, thus enabling faster and more cost-effective execution.

[0015] The aforementioned problem is further solved by a device according to the invention as described in claim 7. The device for analyzing a multi-junction solar cell with at least two sub-junction solar cells using luminescence radiation comprises an excitation unit for applying an electrical voltage to the multi-junction solar cell and / or for subjecting the multi-junction solar cell to electromagnetic excitation radiation in order to generate luminescence radiation in the sub-junction solar cells. Furthermore, the device comprises a receiving unit, which includes a multi-element detector with a plurality of detector elements and is configured to detect the luminescence radiation emitted by the multi-junction solar cell with spatial resolution using the detector elements. The device also comprises an evaluation unit for evaluating the measurement signals from the detector elements.The intensity of the luminescence radiation is attenuated or completely blocked in an overlap spectral region where the sensitivities of at least two groups of detector elements overlap.

[0016] The device is therefore designed to perform an analysis using photoluminescence and / or electroluminescence.

[0017] It is essential that the device is designed to expose a first group of detector elements to a first spectral range of luminescence radiation and at least a second group of detector elements, different from the first group, simultaneously to at least a second spectral range of luminescence radiation, wherein the first and second spectral ranges and optionally further spectral ranges are different.

[0018] This results in the advantages mentioned above in the description of the method according to the invention.

[0019] Advantageously, the measurement signals from the detector elements of the multi-element detector are generated in groups. This allows for a simple allocation of the first group's evaluation to one sub-solar cell and the second group's evaluation to the second sub-solar cell. In particular, it is advantageous that the measurement signals from the first group can be used to analyze one sub-solar cell and the measurement signals from the second group to analyze the other sub-solar cell.

[0020] To perform a fast and uncomplicated analysis, it is advantageous that at least one image of the luminescence radiation is acquired using the multi-element detector, for which the measurement signals of the first group of detector elements and the second group of detector elements are evaluated separately. Furthermore, since the detector elements of the multi-element detector are simultaneously exposed to luminescence emitted by the multi-junction solar cell, a further advantageous embodiment allows for the evaluation of both spectral ranges and thus the analysis of both sub-solar cells with a small number of images, in particular with just one image.

[0021] Investigations by the applicant show that the luminescence radiation from different sub-solar cells is often emitted with varying intensities. To nevertheless enable time-saving simultaneous analysis of both sub-solar cells, the luminescence radiation of the sub-solar cell with the higher intensity is advantageously attenuated selectively. This attenuation is preferably achieved using an optical filter, which preferably reduces the intensity only in the spectral range of the luminescence radiation from the sub-solar cell to be attenuated, preferably by absorption and / or reflection. The intensity can be attenuated by approximately 90% to 99.9% and beyond. In particular, the use of a dielectric filter is within the scope of the invention.

[0022] Investigations by the applicant further show that, although the spectral sensitivities of different groups of detector elements often exhibit different spectral centers and, in particular, different maxima in the spectrum, the sensitivities overlap due to the spectral distribution. The intensity of the luminescence radiation is therefore attenuated or completely blocked in an overlap spectral region where the sensitivities of the groups of detector elements overlap. This attenuation or blocking is preferably achieved by means of an optical filter. Accordingly, the device according to the invention preferably includes an optical filter to suppress overlapping spectral sensitivities of the first and second, and optionally further, groups of detector elements.

[0023] This enables simultaneous analysis of both sub-solar cells, resulting in better separation between the two solar cells, as the luminescence radiation is attenuated in the overlap area.

[0024] Preferred spectral ranges for attenuation or complete blocking are, for example, 800 nm to 950 nm or 1050 nm to 1200 nm. Attenuation in these spectral ranges is preferably achieved by 90% to 99.99% and above.

[0025] As previously explained, it is advantageous to simultaneously measure the luminescence radiation using both the first and second group of detector elements of the multi-element detector. In particular, it is therefore advantageous that, for a given excitation method—by applying excitation radiation to the solar cell and / or applying an electrical voltage to generate the luminescence radiation—the analysis of both sub-solar cells can be performed.

[0026] However, some multi-junction solar cells have sub-solar cells which are advantageously subjected to different excitation conditions to achieve luminescence radiation of sufficient intensity.

[0027] In an advantageous embodiment, therefore, at least a first and a second image with different excitation conditions for generating the luminescence radiation are recorded using the multi-element detector, and the first image is used to analyze one of the sub-solar cells and the second image to analyze the other sub-solar cell.

[0028] Thus, when analyzing one image, only the measurement signals of one of the two groups of detector elements are used, and similarly, when analyzing the other sub-solar cell, only the measurement signals of the other group of detector elements are used. Nevertheless, compared to previously known devices, this method is more time- and cost-effective, since although the acquisition and evaluation of two images from the multi-element detector is necessary, the use of a multi-element detector can be carried out without any mechanical modifications, i.e., without replacing the detector or optical filters.

[0029] The multi-element detector is designed as a color camera with at least two color channels, in particular as a color CCD or CMOS camera. This allows for the cost-effective use of commercially available cameras, which already feature various groups of detector elements of the multi-element detector (especially a CCD or CMOS chip) that are assigned to different spectral ranges, for example, the different color channels, such as an R, a B, and a G color channel in RGB cameras.

[0030] This results in a particularly cost-effective construction.

[0031] Advantageously, the multi-element detector features a Bayer matrix and is therefore designed as a Bayer sensor. This also offers the advantage that such sensors are commercially available and therefore inexpensive, and already incorporate a division into different color channels.

[0032] In a further advantageous embodiment, the multi-element detector is designed as a multi-spectral camera, in particular as a hyperspectral camera.

[0033] Such cameras, which are known per se, have the advantage of being able to divide the signal into a multitude of color channels, thus allowing several color channels to be combined for the analysis of a single sub-solar cell. Advantageously, the detectors of one group of color channels are used to analyze one sub-solar cell, and the remaining detectors are used to analyze the other sub-solar cell.

[0034] Further advantageous features and embodiments of the method and device according to the invention are explained below with reference to exemplary embodiments and the figures.

[0035] Figure 1 shows an embodiment of a device according to the invention.

[0036] In Figure 1A schematic representation shows a first embodiment of a device according to the invention for analyzing a multi-junction solar cell with at least two sub-solar cells using luminescence radiation.

[0037] The device includes an excitation unit 1, which is configured as a light source. The device according to the present embodiment is designed to analyze a photovoltaic multi-junction solar cell 2, which is configured as a tandem solar cell. The tandem solar cell has two superimposed pn junctions in a manner known per se. For this purpose, several layers are arranged on a silicon substrate, including a perovskite layer to form an upper sub-solar cell, while a second, lower sub-solar cell is formed in the silicon substrate.

[0038] The multi-junction solar cell 2 is arranged on a solar cell carrier 3, which is moved perpendicular to the plane of the drawing by means of a conveyor belt in order to move the multi-junction solar cell in an inline manufacturing process.

[0039] The device has a receiver unit 4, which in this case is designed as a commercially available RGB camera without a commercially available infrared blocking filter, which has a CCD or CMOS chip (in this case a CCD chip) which is designed as a Bayer sensor and thus has a Bayer matrix.

[0040] The receiver unit 4 has a lens 4a positioned in front of it for imaging the luminescence radiation emitted by the multi-junction solar cell 2 onto the CCD chip. The lens 4a also has a filter to absorb / reflect (in this case, absorb) the excitation radiation from the excitation unit 1, so that any excitation radiation reflected from the multi-junction solar cell 2 or other objects is not detected by the receiver unit.

[0041] The excitation unit 1 emits excitation radiation with wavelengths of 640 nm and 905 nm, and the aforementioned filter in the objective 4a of the receiving unit 4 is designed accordingly to absorb this radiation.

[0042] The multi-junction solar cell 2, stimulated by excitation radiation via excitation unit 1, emits luminescent radiation from each of its two sub-solar cells due to the excitation. The luminescent radiation from the sub-solar cell formed in the silicon substrate lies essentially in a spectral range of 1000 nm to 1200 nm. The luminescent radiation emitted by the upper sub-solar cell formed by the perovskite layer lies essentially in the spectral range of 700 nm to 850 nm.

[0043] To further achieve a clear separation of the two spectral ranges, the lens 4a also features an optical filter that absorbs radiation in the range of 850 nm to 950 nm, and thus between the two aforementioned spectral ranges. This ensures a clear separation of the two spectral ranges.

[0044] The CCD chip of the receiver unit 4 is designed as a Bayer sensor, as described above, and thus has a large number of detector elements which enable spatially resolved detection of the luminescence radiation and, in addition, detection of the luminescence radiation in three color channels.

[0045] The device has an evaluation unit 5 which is connected to the excitation unit 1 and the receiving unit 4 in order to control the excitation unit 1 to apply excitation radiation to the multiple solar cell 2 and to enhance measurement signals from the multiple solar cell 2.

[0046] The functioning of the device according to the first embodiment is described below with reference to a first embodiment of a method according to the invention: The evaluation unit 5 controls the excitation unit 1 in order to subject the multiple solar cell 2 to excitation radiation as described above, so that both sub-solar cells generate luminescence radiation in one process step.

[0047] In process step B, the luminescence radiation is detected with spatial resolution using the receiving unit 4.

[0048] Crucially, in process step B, the detector elements of the multi-element detector, in this case the individual pixels of the CCD or CMOS chip, are simultaneously illuminated by luminescence radiation emitted by the multi-junction solar cell. A first spectral range is captured using all groups of detector elements assigned to the red, green, and blue color channels, while a second group of detector elements, distinct from the first and assigned to the red color channel, captures a second spectral range. The separation of the two spectral ranges is achieved by analyzing the blue (or green) color channel for the first spectral range and the difference between the red and blue (or green) color channels for the second spectral range.

[0049] To analyze the multi-junction solar cell 2, it is therefore only necessary to take one picture using the receiver unit 4, whereby the measurement signals of the first group of detector elements (the blue color channel) are used to analyze the silicon sub-solar cell and the difference of the measurement signals of the second and third group of detector elements (the red and blue color channels) are used to analyze the silicon sub-solar cells using the evaluation unit 5.

[0050] The analysis of the luminescence radiation can be carried out in a manner known per se, in particular as described in Bolun Du et al. Nondestructive inspection, testing and evaluation for Si-based, thin film and multi-junction solar cells: An overview Renewable and Sustainable Energy Reviews 78 (2017) 1117-1151 or for the analysis of material parameters as described in DE 10 2010 019 132.

[0051] In a modification of the first embodiment, the device includes an excitation unit 1a, which is connected to electrical contacts of the multi-junction solar cell 2 and is configured to apply an electrical voltage to the multi-junction solar cell 2 in order to generate luminescent radiation in the sub-junction solar cells. The excitation unit 1a is connected to the evaluation unit 5 and is controlled by it to carry out the aforementioned method. Reference symbol list

[0052] 1, 1aExcitation unit 2Multiple solar cell 3Solar cell carrier 4Receiving unit 4aLens 5Evaluation unit

Claims

1. A method for the analysis of a multiple solar cell (2) with at least two sub-solar cells by means of luminescence radiation with the method steps: A. Generating luminescence radiation in the sub-solar cells by applying excitation radiation to the multiple solar cell (2) and / or applying an electrical voltage to contacts of the multiple solar cell (2); B. Spatially resolved detecting the luminescence radiation by means of at least one multi-element detector with a plurality of detector elements and evaluating different spectral ranges of the luminescence radiation for the different sub-solar cells, wherein the multi-element detector is designed as a color camera with at least two color channels and in method step B, the detector elements are simultaneously exposed to luminescence radiation radiated from the multiple solar cell (2), wherein a first spectral region is detected by means of a first group of detector elements and at least a second spectral region is detected by means of at least a second group different from the first group of detector elements, wherein the first and second spectral regions are different and spectral sensitivities of different groups of detector elements have different spectral focal points and overlap, and wherein the intensity of the luminescence radiation in an overlapping spectral region, In which the sensitivity of at least two groups of detector elements overlap, is attenuated or completely blocked.

2. The method according to claim 1, characterized in that the measurement signals of the detector elements of the multi-element detector are evaluated in groups, in particular, in that the measurement signals of the first group for the analysis of a sub-solar cell and the measurement signals of the second group for the analysis of the other sub-solar cell and preferably the measurement signals of further groups for the analysis of the further sub-solar cells are used and / or preferably a combination of the measurement signals of several groups, in particular, a subtraction of the measurement signals from two or more groups, is used for the analysis of a sub-solar cell.

3. The method according to any one of the preceding claims, characterized in that by means of the multi-element detector at least one image of the luminescence radiation is recorded, for which the measurement signals of the first group of detector elements and at least the second group of detector elements are evaluated separately in groups.

4. The method according to any one of the preceding claims, characterized in that the luminescence radiation of a sub-solar cell is selectively attenuated, the luminescence radiation of which has a higher intensity compared to the other sub-solar cell, in particular by means of an optical filter.

5. The method according to any one of the preceding claims, characterized in that the intensity of the luminescence radiation in the overlapping spectral region, in which the sensitivity of the at least two groups of detector elements overlap, is attenuated by means of an optical filter or is completely blocked.

6. The method according to any one of the preceding claims, characterized in that by means of the multi-element detector at least a first and a second image with different excitation conditions for generating the luminescence radiation are recorded and the first image is used for the analysis of one of the sub-solar cells and the second image is used for the analysis of the other sub-solar cell.

7. A device for the analysis of a multiple solar cell (2) with at least two sub-solar cells by means of luminescence radiation, with an excitation unit (1, 1a) for applying an electrical voltage to the multiple solar cell (2) and / or for applying electromagnetic excitation radiation to the multiple solar cell (2) in order to generate luminescence radiation in the sub-solar cells, with a receiving unit (4), which has at least one multi-element detector having a plurality of detector elements and is designed to detect luminescence radiation emitted by the multi-solar cell (2) spatially resolved by means of the detector elements and with an evaluation unit (5) for evaluating the measurement signals of the detector elements, wherein the device is designed to apply to a first group of detector elements a first spectral region of the luminescence radiation and to at least a second group, different from the first group of detector elements, simultaneously at least a second spectral region of the luminescence radiation, wherein the first and second and preferably further spectral regions are different and spectral sensitivities of different groups of detector elements have different spectral focal points and overlap and the multi-element detector is designed as a color camera with at least two color channels, wherein the intensity of the luminescence radiation in an overlapping spectral region, in which the sensitivity of at least two groups of detector elements overlap, is attenuated or completely blocked.

8. The device according to claim 7, characterized in that the multi-element detector is designed as a color CCD or CMOS camera.

9. The device according to any one of claims 7 to 8, characterized in that the multi-element detector has a Bayer matrix.

10. The device according to any one of claims 7 to 9, characterized in that the multi-element detector is designed as a multispectral camera, in particular as a hyperspectral camera.

11. The device according to any one of claims 7 to 10, characterized in that the luminescence radiation of a sub-solar cell is selectively attenuated, the luminescence radiation of which has a higher intensity compared to the other sub-solar cell, in particular by means of an optical filter.

12. The device according to any one of claims 7 to 11, characterized in that the intensity of the luminescence radiation in an overlapping spectral region, in which the sensitivity of the at least two groups of detector elements overlap, is attenuated by means of an optical filter or is completely blocked.