Method for inspecting a photovoltaic device and a photovoltaic device inspected using such a method

Abstract

The present invention relates to a method for inspecting a photovoltaic element (1), preferably to identify the output of the photovoltaic element (1) and / or to identify defects therein, and to a photovoltaic element (1) inspected using such a method.

Description

[Technical Field]

[0001] The present invention relates to a method for inspecting photovoltaic elements, in particular for inspecting manufacturing quality and / or determining the optical and / or electrical properties of the elements, and to photovoltaic elements inspected using such a method. [Background technology]

[0002] For electrical characterization, a solar cell must be illuminated uniformly and over its entire surface with sunlight-like illumination (Standard Test Conditions - STC), and the resulting current and voltage must be measured at appropriate contacts. A solar simulator, known as a flasher, reproduces the spectral width and intensity distribution of sunlight in this case. The solar simulators used for illumination are very complex in terms of instrumentation and cannot be adjusted in length. Typical solar simulators illuminate an area of ​​up to 3 m2. The illumination area of ​​a solar simulator used to characterize solar cell performance is finite, and it is not possible to illuminate the entire solar cell area at once, especially for particularly large and long solar cells. Measurements of natural sunlight are highly error-prone and cannot be achieved with reasonable throughput.

[0003] During testing, it is technically not feasible to uniformly illuminate a solar cell with any length and / or width as required by relevant standards, e.g., Non-Patent Document 1. Testing cannot be performed on solar cells with lengths and / or widths that exceed the illumination area of ​​the solar simulator.

[0004] Patent document 1 discloses a test system for inspecting the manufacturing quality of solar cells, which includes an optical test device arranged in a test area for visually inspecting the solar cells, an electrical test device with a lighting device that irradiates the solar cells with light for testing the electrical functions of the solar cells, and an electrical contact device that taps off the voltage at the contacts of the solar cells.

[0005] Patent Document 2 discloses a solar cell inspection device that includes a solar simulator, a light intensity control unit connected to the solar simulator and controlling the amount of light emitted by an array of light-emitting elements in the solar simulator, and an electrical measurement unit electrically connected to the solar cell and having a light-receiving area positioned over at least a portion of the effectively irradiated area of ​​the solar simulator, for measuring the photoelectric conversion characteristics of the solar cell while an electrical load is applied to the solar cell.

[0006] The methods for testing solar cells known from the prior art do not allow testing solar cells of any size, in particular because they depend on the size of the area illuminated by the solar simulator. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent Application Publication No. 1647827 [Patent Document 2] German Patent Application Publication No. 112011100041 [Patent Document 3] International Publication No. 2004 / 083958 [Patent Document 4] International Publication No. 2011 / 161108 [Patent Document 5] International Publication No. 2006 / 092134 [Patent Document 6] International Publication No. 2014 / 206860 [Non-patent literature]

[0008] [Non-Patent Document 1] IEC60904 [Non-patent document 2] IEC60904-1:2006 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention is therefore based on the object of providing a method for measuring and inspecting photovoltaic elements that are larger, in particular longer and / or wider, compared to the illumination area of ​​a solar simulator, and which does not suffer from the above-mentioned drawbacks, and in particular in which the overall characteristic curve and / or the overall photocurrent of the entire photovoltaic element is ascertained over an area larger than the area illuminated by the solar simulator. [Means for solving the problem]

[0010] This object is achieved by the subject matter of the independent claims. Advantageous refinements emerge from the dependent claims.

[0011] This object is achieved by providing a method for inspecting photovoltaic elements, preferably to determine the performance of the photovoltaic elements and / or to identify defects therein, the method comprising: a) providing a photovoltaic element; b) providing a dark characteristic curve of the photovoltaic element at a particular voltage applied to the photovoltaic element; c) dividing the photovoltaic elements into individual segments; d) measuring the characteristic curves of individual segments of the photovoltaic element in a time sequence, the individual segments being illuminated by a lighting device with a specific voltage applied to the photovoltaic element, the photovoltaic element being moved along a direction of travel relative to the lighting device and / or the lighting device being moved along a direction of travel relative to the photovoltaic element; e) determining the overall characteristic curve of the photovoltaic element according to the dark characteristic curve and the measured characteristic curves of the individual segments, so that the photovoltaic element can be inspected; Includes.

[0012] Preferably, an overall photocurrent for the entire photovoltaic element is obtained, the overall photocurrent being obtained from the sum of all of the photocurrents of the individual segments.

[0013] The method according to the invention makes it theoretically possible to inspect photovoltaic elements of any length and / or width, in particular through segment-by-segment illumination and mathematical synthesis of the overall characteristic curve. Thus, the photovoltaic element is not illuminated and measured over its entire area, but rather the overall measurement is synthesized from several individual measurements with illumination of individual segments. Thus, for example, the requirement in conventional standards that the photovoltaic element must be fully illuminated during measurement is not met. However, dividing the photovoltaic element into individual segments and measuring these uniformly illuminated individual segments with the method according to the invention results in no deviations, or at least only slight deviations, compared to full-area illumination of the entire photovoltaic element. Thus, the method according to the invention makes it possible to inspect photovoltaic elements of almost any length and / or width, thereby leading to their certification.

[0014] In one preferred embodiment of the present invention, the particular applied voltage is a particular voltage profile, and the current in the photovoltaic elements and / or individual segments is preferably measured in response to the particular voltage profile.

[0015] Dividing the photovoltaic elements into individual segments is understood to mean in particular the logical division of the photovoltaic elements into individual segments.

[0016] Measuring the characteristic curves of individual segments of a photovoltaic element in a time sequence is understood to mean, in particular, that the characteristic curves of at least two mutually adjacent segments of a photovoltaic element are measured in seamless time succession.

[0017] A dark characteristic curve is understood to mean in particular the characteristic curve when the photovoltaic element is at least approximately darkened, preferably when the photovoltaic element is completely darkened.

[0018] For the present invention, the characteristic curve is Ph (V) on the applied voltage, ie the photocurrent-voltage characteristic curve of a photovoltaic element or a segment of a photovoltaic element.

[0019] In one preferred embodiment of the invention, the characteristic curve of a segment is ascertained from the dark characteristic curve and the characteristic curve of that segment when illuminated. In one preferred embodiment of the invention, the overall characteristic curve of the photovoltaic element is ascertained from the dark characteristic curve and the characteristic curves of the individual illuminated segments.

[0020] In one preferred embodiment of the invention, the photocurrent of a segment is determined from the dark characteristic curve and the characteristic curve of that illuminated segment. In one preferred embodiment of the invention, the overall characteristic curve is determined from the photocurrents of the individual segments and the dark characteristic curve of the photovoltaic element, and the overall photocurrent of the photovoltaic element is preferably determined from the sum of the photocurrents of the individual segments.

[0021] In one preferred embodiment of the invention, the characteristic curves of the individual segments of the photovoltaic element are measured discontinuously, in particular in steps.

[0022] In one alternative embodiment of the present invention, the characteristic curves of the individual segments of the photovoltaic element are measured continuously.

[0023] In one preferred embodiment of the present invention, the splitting of the photovoltaic elements in step b) and the movement of the photovoltaic elements along the direction of travel relative to the lighting device and / or the movement of the lighting device along the direction of travel relative to the photovoltaic elements in step c) are performed at least partially simultaneously.

[0024] In one preferred embodiment of the invention, the lighting device is a solar simulator.

[0025] In one preferred embodiment of the invention, the individual segments of the photovoltaic elements are illuminated with their photoactive areas parallel to the lighting device, in particular parallel to the light source of the lighting device.

[0026] Photovoltaic elements are understood to mean in particular solar cells, which have at least one photovoltaic cell, and preferably have a plurality of photovoltaic cells, which can be arranged and / or interconnected in different ways in the photovoltaic element.

[0027] In one preferred embodiment of the invention, the photovoltaic element comprises at least two photovoltaic cells, which are connected in parallel and / or in series with each other, either successively in the direction of successive segments, in particular continuously conducting, or formed from cells interconnected in parallel with each other in the direction of successive segments, the photovoltaic cells preferably being formed over the entire length of the photovoltaic element and / or the photovoltaic cells being interconnected in parallel with each other over the entire length of the photovoltaic element.

[0028] In one preferred embodiment of the present invention, the photovoltaic element is divided into segments so that all photovoltaic cells connected in series have the same surface area in each individual segment.

[0029] In one preferred embodiment of the present invention, the photovoltaic device is an organic photovoltaic device, and at least one photoactive layer of the organic photovoltaic device preferably has a small molecule as the absorbing material.

[0030] In one preferred embodiment of the present invention, the photovoltaic element is a flexible photovoltaic element, in particular a flexible organic photovoltaic element.

[0031] In one preferred embodiment of the present invention, the photovoltaic device comprises at least one photovoltaic cell with at least one photoactive layer, in particular a CIS, CIGS, GaAs, or Si cell, a perovskite cell, or an organic photovoltaic device (OPV). Organic photovoltaic devices are understood to mean, in particular, photovoltaic devices with at least one organic photoactive layer, in particular polymer organic photovoltaic devices or organic photovoltaic devices based on small molecules. Polymers are distinguished by being nonvolatile and therefore only applicable from solution, whereas small molecules are usually volatile and can be applied not only from solution, like polymers, but also by vapor deposition techniques, in particular vacuum deposition. Small molecules are understood to mean non-polymerizable organic molecules with a monodisperse molar mass of 100 to 2000 g / mol that exist in the solid phase at standard pressure (ambient atmospheric pressure) and room temperature. In particular, small molecules are photoactive, where "photoactive" means that the charge state and / or polarization state of the molecule changes when exposed to light.

[0032] In one preferred embodiment of the invention, the photoactive layer of the layer system comprises small molecules which evaporate in vacuum.In one preferred embodiment of the invention, at least the photoactive layer of the layer system is vapor deposited in vacuum.

[0033] One possible structure of the layer system of an optoelectronic component is described in Patent Documents 3 and 4. Preferably, a layer system is used in which the photoactive layer is volatile and is deposited by physical vapor deposition (PVD) or contains a previously deposited absorbing material. Materials belonging to the group of small molecules, as described, inter alia, in Patent Documents 5 and 6, are used for this purpose. The photoactive layer forms an acceptor / donor system and can be several individual layers or mixed layers as a planar heterojunction, preferably a bulk heterojunction. Layer systems in which deposition is completed by physical vapor deposition are preferred.

[0034] The method according to the invention for inspecting photovoltaic elements has advantages over the prior art. Advantageously, it allows photovoltaic elements of almost any length and / or width to be inspected by means of an illumination device. Advantageously, the method is easy and cheap to use. Advantageously, it allows areas of almost any size of a photovoltaic element to be inspected. This advantageously allows long photovoltaic elements, including in particular those having a length and / or width of more than 2 m, to be measured in accordance with usual standards, for example according to Non-Patent Document 2.

[0035] According to one development of the invention, the individual segments are illuminated over their entire area, preferably over their entire photoactive area, and / or the individual segments of the photovoltaic elements and / or the individual segments themselves are each illuminated at least approximately uniformly.

[0036] Uniform illumination is understood to mean illumination that is as uniform as possible over the segment, in particular over the area of ​​the segment, preferably over the entire area of ​​the segment.

[0037] According to one development of the invention, the overall characteristic curve of the photovoltaic element is determined by e) summing up the photocurrents determined from the dark characteristic curve of the photovoltaic element and the measured characteristic curves of the individual segments.

[0038] Summing the characteristic curves is also to be understood as meaning in particular to combine the characteristic curves, wherein the determined photocurrent of at least one further characteristic curve in ambient light is further subtracted in particular from the determined photocurrent of the illuminated characteristic curve.

[0039] According to one development of the invention, the segments of the photovoltaic element have at least approximately no overlap with the preceding and / or succeeding segments in the direction of travel and at least approximately no gaps, which ensures that no area of ​​the photovoltaic element, in particular no photoactive area, is measured twice and / or that parts of the area of ​​the photovoltaic element are not measured.

[0040] According to one development of the invention, the photovoltaic element, preferably the photoactive area of ​​the photovoltaic element, is provided to be completely covered by the individual segments.

[0041] According to one development of the invention, the dark characteristic curve of the photovoltaic element is provided, preferably measured, in step b) before step d) of the method or after step d), and / or steps c) and d) are performed together. In one preferred embodiment of the invention, the dark characteristic curve of the photovoltaic element is measured. In an alternative preferred embodiment of the invention, the dark characteristic curve of the photovoltaic element is already known.

[0042] According to one development of the invention, the dark characteristic curve of the photovoltaic element in step b) is provided to be the dark characteristic curve in complete or almost complete darkness.

[0043] According to one development of the invention, when ambient light is present, at least one further characteristic curve is measured at a specific voltage applied to the photovoltaic element and in ambient light, the individual segments and / or the photovoltaic element are not illuminated by the lighting device, and the overall characteristic curve of the photovoltaic element is further determined in step e) as a function of the at least one further characteristic curve in ambient light and / or the overall characteristic curve of the photovoltaic element is determined in step e) by further subtracting the determined ambient light photocurrent from the further measured characteristic curve of the individual segment in ambient light.

[0044] Ambient light is understood to mean the ambient light present when measuring the dark characteristic curves of the photovoltaic elements and / or the dark characteristic curves of the individual segments of the photovoltaic elements and / or when measuring the characteristic curves of the photovoltaic elements and / or the characteristic curves of the individual segments of the photovoltaic elements under illumination by a lighting device, in particular when the environment is not completely dark. In this case, the ambient light generates an additional photocurrent of the photovoltaic elements and / or the individual segments of the photovoltaic elements, thereby affecting the determination of the overall photocurrent. The intensity of the ambient light is particularly significantly lower than the intensity of the illumination by the lighting device, preferably at most 10%, preferably at most 8%, preferably at most 5% or preferably at most 2% of the intensity of the illumination by the illumination light.

[0045] According to one embodiment of the invention, the length of the segments in the direction of travel is between 10 cm and 10 m, preferably between 10 cm and 2 m, and / or the photovoltaic elements are divided into individual segments depending on the area illuminated by the lighting device.

[0046] In one preferred embodiment of the invention, the length of the individual segments in the direction of travel is 10 cm to 10 m, preferably 10 cm to 5 m, preferably 10 cm to 2 m, preferably 10 cm to 1 m, preferably 20 cm to 10 m, preferably 20 cm to 5 m, preferably 20 cm to 2 m or preferably 20 cm to 1 m or at least 10 cm, preferably at least 20 cm, preferably at least 60 cm, preferably at least 1 m or preferably at least 2 m. In one particularly preferred embodiment of the invention, the length of the individual segments is at least 1 / 20, preferably at least 1 / 10 or preferably at least 1 / 8 of the length of the photoactive area of ​​the photovoltaic element.

[0047] The length of a photovoltaic element and / or a segment of a photovoltaic element may alternatively be understood to mean in particular the width of a segment of a photovoltaic element, the length and / or width preferably being independent of the direction of travel relative to the lighting device.

[0048] According to one development of the invention, the method is carried out in a roll-to-roll process and / or the photovoltaic element is a flexible photovoltaic element, and during the method the first end and / or the second end of the photovoltaic element is preferably in a partially or fully rolled-up form.

[0049] The object of the present invention is also achieved by providing a photovoltaic element that is inspected using the method according to the invention, in particular one of the exemplary embodiments described above, in which case the advantages already explained for the method for inspecting a photovoltaic element are also obtained in particular for the photovoltaic element.

[0050] The invention will now be described in detail with reference to the following drawings: [Brief explanation of the drawings]

[0051] [Figure 1] 1 is a flow chart illustrating a schematic diagram of one exemplary embodiment of a method for inspecting photovoltaic devices. [Figure 2] 1 is a plan view of a schematic diagram of one exemplary embodiment of a plurality of arrangements of photovoltaic elements relative to a lighting device during a method of inspecting the photovoltaic elements; [Figure 3] FIG. 1 is a plan view of a schematic diagram of one exemplary embodiment of dividing a photovoltaic element into individual segments. [Figure 4] 1 is a side view of a schematic diagram of one exemplary embodiment of an apparatus for performing a method of inspecting photovoltaic elements; [Figure 5] 3 shows an exemplary embodiment of the overall characteristic curve of a photovoltaic element ascertained from the dark characteristic curves and characteristic curves of the individual segments using the method according to the invention; FIG. [Figure 6] 10A-10C illustrate exemplary embodiments of the influence of the positioning of the individual segments when dividing the photovoltaic element in a method according to the present invention. [Figure 7] 10A-10C illustrate an exemplary embodiment of the effect of segment length when dividing a photovoltaic element in a method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0052] FIG. 1 shows in flow chart form a schematic diagram of one exemplary embodiment of a method for inspecting photovoltaic devices.

[0053] If the photovoltaic device 1 is larger than the illumination area of ​​the solar simulator, direct performance measurement is not possible. Electrical functional testing of the photovoltaic device 1 is possible by illuminating only a portion of the photovoltaic device 1 divided into individual segments 5 each time, checking the characteristic curves 7 of the individual segments 5, and then reconstructing or synthesizing the overall characteristic curve 13.

[0054] A method for inspecting a photovoltaic element 1, preferably to identify the performance of the photovoltaic element 1 and / or to identify defects therein, includes the steps of: a) providing a photovoltaic element 1; b) providing a dark characteristic curve 3 of the photovoltaic element 1 at a specific voltage applied to the photovoltaic element 1; c) dividing the photovoltaic element 1 into individual segments 5; d) measuring the characteristic curves 7 of the individual segments 5 of the photovoltaic element 1 in a time sequence, wherein the individual segments 5 are illuminated by a lighting device 9 at a specific voltage applied to the photovoltaic element 1, and the photovoltaic element 1 is moved along a direction of travel 11 relative to the lighting device 9, and / or the lighting device 9 is moved along the direction of travel relative to the photovoltaic element 1; and e) confirming an overall characteristic curve 13 of the photovoltaic element 1 according to the dark characteristic curve 3 and the measured characteristic curves 7 of the individual segments 5, whereby the photovoltaic element 1 can be inspected.

[0055] The photovoltaic element 1 is in this case guided in particular in the direction of travel 11 within the production device.

[0056] This allows photovoltaic elements 1 of almost any length and / or width to be inspected by the lighting device 9. The method is easy and cheap to use, which advantageously allows the measurement of long and / or large photovoltaic elements 1, including in particular those whose length and / or width exceeds 2 m.

[0057] In one refinement of the invention, the individual segments 5 are illuminated over their entire area 15, preferably over their entire photoactive area, and / or the individual segments 5 of the photovoltaic element 1 and / or the individual segments 5 of themselves are each illuminated at least approximately uniformly.

[0058] In a further refinement of the invention, the overall characteristic curve 13 of the photovoltaic element 1 is determined by e) summing the photocurrents determined from the dark characteristic curve 3 of the photovoltaic element 1 and the measured characteristic curves 7 of the individual segments 5.

[0059] In a further refinement of the invention, the segments 5 of the photovoltaic element 1 have at least approximately no overlap with the preceding segment 5 and / or the succeeding segment 5 in the direction of travel 11 and are at least approximately free of gaps.

[0060] In a further refinement of the invention, the photovoltaic element 1, preferably the photoactive area of ​​the photovoltaic element 1, is completely covered by the individual segments 5.

[0061] In a further refinement of the invention, the dark characteristic curve 3 of the photovoltaic element 1 is provided and preferably measured in step b) before step d) of the method or after step d), and / or steps c) and d) are performed together.

[0062] In a further refinement of the invention, the dark characteristic curve 3 of the photovoltaic element 1 in step b) is the dark characteristic curve 3 in complete or almost complete darkness.

[0063] In a further refinement of the invention, when ambient light is present, at least one further characteristic curve 17 is measured at a specific voltage applied to the photovoltaic element 1 and in ambient light, the individual segments 5 and / or the photovoltaic element 1 are not illuminated by the lighting device 9, and the overall characteristic curve 13 of the photovoltaic element 1 is further determined in step e) according to the at least one further characteristic curve 17 in ambient light, and / or the overall characteristic curve 13 of the photovoltaic element 1 is determined in step e) by further subtracting the determined ambient light photocurrent from the further measured characteristic curve 17 of the individual segments 5 in ambient light.

[0064] In a further refinement of the invention, the length of the segment 5 in the direction of travel 11 is between 10 cm and 10 m, preferably between 10 cm and 2 m, and / or the photovoltaic element 1 is divided into individual segments 5 according to the area 19 illuminated by the lighting device 9. In one alternative refinement of the invention, the length of the individual segment is at least 1 / 10 of the length of the photoactive area of ​​the photovoltaic element.

[0065] In a further refinement of the invention, the method is carried out in a roll-to-roll process and / or the photovoltaic element 1 is a flexible photovoltaic element 1, and during the method the first end and / or the second end of the photovoltaic element 1 is preferably present in a partially rolled-up form.

[0066] 2 shows in plan view a schematic diagram of one exemplary embodiment of multiple arrangements of photovoltaic elements 1 relative to a lighting device 9 during a method of testing the photovoltaic elements 1. Identical and functionally equivalent elements are provided with the same reference numerals, and therefore reference is made to the above description in this regard.

[0067] In a first step A, in this exemplary embodiment, a first segment 5.1 of the photovoltaic element 1 at one end of the photovoltaic element 1 is illuminated by the lighting device 9, and with a specific voltage applied to the photovoltaic element 1, the characteristic curve 7 of the first segment 5.1 is measured, in particular the photocurrent, while the other segments 5 are at least generally darkened. The specific voltage can be applied to the photovoltaic element 1 via the connecting element 20.

[0068] In a further step B, the photovoltaic element 1 is moved relative to the lighting device 9 in the direction of travel 11, so that a second segment 5.2 of the photovoltaic element 1 is illuminated by the lighting device 9. One end of the photovoltaic element 1, on which the first segment 5.1 is arranged, can in this case be at least partially wound around a winding element. As in step A, in step B, with a certain voltage applied to the photovoltaic element 1, the characteristic curve 7 of the second segment 5.2 is also determined, in particular the photocurrent, while the other segments 5 are at least largely darkened. Depending on the length of the photovoltaic element 1 and the final number of individual segments 5, the method is carried out until all characteristic curves 7, in particular the photocurrent, of the individual segments 5 have been measured. In this exemplary embodiment, the individual segments 5 were illuminated with 1000 W / m2. The photovoltaic element 1 is divided into individual segments 5 in this case, in particular so that there are at least approximately no gaps between consecutive individual segments 5 on the photovoltaic element 1, for example between a first segment 5.1 and a second segment 5.2, and so that there is at least approximately no overlap between consecutive segments 5 on the photovoltaic element 1, for example between a first segment 5.1 and a second segment 5.2. The length of the individual segments 5 can be adjusted in this case to the area 19 of the lighting device 9. One end of the segment 5 does not need to be in seamless contact with both ends of the photovoltaic element 1, since photocurrent is generated only in the active area of ​​the photovoltaic element 1. Each area of ​​the photovoltaic element 1 can be illuminated only once.

[0069] In step C, measurements are completed on the photovoltaic element 1, which in this exemplary embodiment is in a fully wound form. The dark characteristic curve 3 required for this method can be obtained by measuring the characteristic curve of the photovoltaic element 1, in particular of the entire photoactive area of ​​the photovoltaic element, at a specific voltage, without illumination, in particular without ambient light, in the darkest possible conditions, for example in the wound state of the photovoltaic element 1. The overall characteristic curve 13 of the photovoltaic element 1 is synthesized from the measured characteristic curves 7 and the dark characteristic curve 3 of the individual segments 5.

[0070] In one exemplary embodiment, the photovoltaic element 1 consists of a succession of thin layers, the layer system having at least one photoactive layer being preferably vacuum-deposited or processed from solution. The electrical link may be implemented by a metal layer, a transparent conductive oxide and / or a transparent conductive polymer. The photovoltaic element 1 may be a flexible photovoltaic element 1 and may be present during or at the end of the method in an at least partially rolled-up form.

[0071] 3 shows in plan view a schematic diagram of one exemplary embodiment of the division of a photovoltaic element 1 into individual segments 5. Identical and functionally equivalent elements are provided with the same reference numerals, and in this regard reference is therefore made to the above description.

[0072] In this exemplary embodiment, the photovoltaic element 1 is divided into individual segments 5.1, 5.2, 5.3, 5.4. The individual segments 5 in this case have different lengths in the direction of travel of the photovoltaic element 1, for example, segments 5.2, 5.3 are the same length, while segments 5.1, 5.4 are shorter in comparison. In this way, the individual segments 5 are completely illuminated in time sequence by areas 19 of the lighting device 9.

[0073] In this exemplary embodiment, the photovoltaic element 1 is manufactured and / or measured in a roll-to-roll process. The first end of the photovoltaic element 1 and / or the second end of the photovoltaic element 1 are present in an at least partially wound form during the method, and the segments 5 to be measured are present in an unwound form, so that the characteristic curves of the segments 5 can be measured under illumination by the lighting device 9. When measuring the individual segments 5, a characteristic voltage is applied to the photovoltaic element 1 and the photocurrent is ascertained according to the voltage profile.

[0074] 4 shows in side view a schematic diagram of one exemplary embodiment of an apparatus for carrying out the method for inspecting photovoltaic elements 1. Identical and functionally equivalent elements are provided with the same reference numerals, and therefore reference is made in this respect to the above description.

[0075] In this exemplary embodiment, an apparatus designed to perform the method according to the invention comprises an illumination device 9 for illuminating the photovoltaic elements 1, a coating device 22 for defining an illumination area 19 by the illumination device 9, an electrical connection element 20 for applying a specific voltage to the photovoltaic elements 1, and a transport unit 24 with two winding elements for moving the photovoltaic elements 1. The apparatus is particularly designed for a roll-to-roll process, and the photovoltaic elements 1 are moved in particular relative to the illumination device 9. Within the area of ​​the illumination device 9, the segments 5 located there are arranged as flat as possible, and their surface facing the illumination device 9 has a photoactive layer. The transport unit 24 moves the photovoltaic elements such that after one segment 5 is measured, the next segment 5 is moved under the illumination device 9. The coating device 22 allows the individual segments 5 to be illuminated separately from one another by the illumination device 9, so that the individual segments 5 can be measured in a time sequence.

[0076] In this case, the photovoltaic element 1 is divided into individual segments 5 and measured. For this purpose, each segment 5 is illuminated by a lighting device 9 and a coating device 22, preferably an aperture mat, arranged between the lighting device 9 and the photovoltaic element 1. The coating device 22 is then moved relative to the photovoltaic element 1, or the photovoltaic element 1 is moved relative to the coating device 22, and all of the individual segments 5, i.e. the entire photovoltaic element 1, are measured in this way. If the dark characteristic curve 3 is still not available, the individual segments 5 or the entire photovoltaic element 1 can be measured in the dark, without illumination, to obtain the dark characteristic curve 3. The overall characteristic curve 13 is obtained from the dark characteristic curve 3, which is the same for all measurements, and the characteristic curves 7 of the individual segments 5.

[0077] In one refinement, the device for carrying out the method further comprises a test device (not shown) arranged in the area of ​​the device for measuring and / or inspecting the individual segments 5 and the photovoltaic elements 1. The test device is in this case operatively connected to the lighting device 9, the coating device 22 and the connecting element 20 and / or the transport unit 24.

[0078] In this exemplary embodiment, the photovoltaic element 1 may be at least partially wound up on winding elements at both ends, with the photovoltaic element 1 then being disposed between the winding elements. In order to move the photovoltaic element 1 relative to the lighting device 9 within the device, the photovoltaic element 1 is wound up or unwound.

[0079] 5 shows one exemplary embodiment of the overall characteristic curve 13 of a photovoltaic element 1 ascertained using the method according to the invention from the dark characteristic curve 3 and the characteristic curves 7 of the individual segments 5. Identical and functionally equivalent elements are provided with the same reference symbols, and in this respect reference is therefore made to the above description.

[0080] The principle of the method according to the invention is illustrated in one exemplary embodiment in Figure 5, where the overall characteristic curve 13 of the photovoltaic element 1 is synthesized from the characteristic curves 7 of the individual segments 5 and the dark characteristic curve 3 of the photovoltaic element 1. The length of the photoactive area of ​​the photovoltaic element 1 is 1934 mm, and the photovoltaic element 1 is divided into individual segments 5 such that the segments 5 at both ends of the photovoltaic element 1 are formed with lengths of 100 mm and 16 mm, which are somewhat shorter than the six intermediate segments 5, each with a length of 303 mm.

[0081] In Figure 5A, the dark characteristic curve 3 and the characteristic curves 7 of all the individual segments 5 of the illuminated photovoltaic element 1 are plotted. For clarity, the enlarged portion shows the profiles of the characteristic curves 7 of the segments 5 that are close to each other.

[0082] In FIG. 5B, the photocurrents ascertained from all characteristic curves 7 of the individual segments 5 under illumination (see FIG. 5A) are plotted, and the photocurrent of the dark characteristic curve 3 of the photovoltaic element 1 is subtracted from the photocurrent of the characteristic curve 7 of the illuminated individual segments 5, thereby obtaining the photocurrent I of the individual segments 5. Ph,s (V) is obtained. For clarity, the enlarged portion shows the photocurrent profile of segments 5 close to each other.

[0083] In Figure 5C, the dark characteristic curve 3 of the photovoltaic element 1, the sum of all the light currents of the individual segments 5 (see Figure 5B) and the overall characteristic curve 13 of the photovoltaic element 1 synthesized from these are plotted.

[0084] The photovoltaic element 1 has two current-voltage characteristic curves, namely the dark characteristic curve 3 I D The current obtained when the photovoltaic element 1 is illuminated can be described by the photocurrent I(V) and the characteristic curve I(V) under illumination. Ph (V) I(V)=I D (V)+I Ph (V) (1) is.

[0085] The overall characteristic curve 13 of the photovoltaic element 1 can be synthesized from the characteristic curves 7 of the individual segments 5, and the photocurrent I Ph,S (V) are specifically summed to give the overall photocurrent I of the photovoltaic element 1. Ph (V) is obtained.

number

[0086] The overall characteristic curve I(V) of a fully illuminated photovoltaic element 1 is therefore the same as the measured characteristic curve 7 I(V) of an illuminated individual segment 5 of the photovoltaic element. s (V) and dark characteristic curve 3 I D (V)

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[0087] Under non-ideal conditions, when measuring the dark characteristic curve 3 and / or the characteristic curve 7 of the individual segment 5, there is interfering ambient light, in particular scattered light. As a result, when measuring the dark characteristic curve 3, the photovoltaic element 1 is not completely dark, resulting in an additional current at least partly from the ambient light and / or when measuring the characteristic curve 7 of the individual segment 5 under illumination with additional ambient light, there is an additional photocurrent, which distorts the identified photoelectric current, in particular to the same extent. In one refinement of the invention, this photocurrent further resulting from the ambient light is taken into account when determining the dark characteristic curve 3 and / or the characteristic curve 7 of the individual segment 5 by summing up the respective additional characteristic curve 17, from which the photocurrent I Ph,amb (V) is confirmed depending on the ambient light.

[0088] During the determination of the dark characteristic curve 3, if the individual segments 5 are not completely darkened, for example by ambient light, in particular by scattered light, the additional photocurrent IPh,amb (V) flows in response to ambient light, which are summed to give the obtained photocurrent from illuminating the individual segments 5. I(V)=I D (V)+I Ph (V)+I Ph,amb (V) (4)

[0089] The characteristic curve 7 I(V) of the illuminated individual segment 5 is given by the following formula:

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[0090] The overall characteristic curve 13 I(V) of the photovoltaic element 1 is 2 ) and under ambient light. D( V) is all that is needed to ascertain the overall characteristic curve 13 of the photovoltaic element 1. This dark characteristic curve 3 can either be already available or can be provided from data measured at a point in the method before the overall characteristic curve 13 is ascertained in step e). The dark characteristic curve 3 does not have to be measured for each individual segment 5.

[0091] The current in each individual segment 5 is I S( V)=I D (V)+I Ph (V)+I Ph,amb (V) (7) is.

[0092] The overall current in the photovoltaic element 1 is therefore: I(V)=I D (V)+Σ S [I S(V)-I amb,s (V)] (8) is.

[0093] 6 shows an exemplary embodiment of the influence of the positioning of the individual segments 5 when dividing the photovoltaic element 1 in the method according to the invention. Identical and functionally equivalent elements are provided with the same reference numerals, and therefore, in this respect, reference is made to the above description.

[0094] The effect of the positioning of the individual segments 5 when dividing the photovoltaic element 1 was investigated. The characteristic curves 7 of the individual segments 5 and the overall characteristic curves 13 of the photovoltaic element 1 with different positioning of the individual segments 5 are shown in FIGS. 6A and 6B. In FIG. 6A, the length of the first segment 5 is 100 mm, the length of each of the next six segments 5 is 303 mm, and the length of the last segment 5 is 16 mm. In FIG. 6B, the length of the first segment 5 is 296 mm, the length of each of the next five segments 5 is 303 mm, and the length of the last segment 5 is 127 mm.

[0095] With any positioning of the individual segments 5 when dividing the photovoltaic element 1, the resulting characteristic curve 13 corresponds to the respective reference characteristic curve. The reference characteristic curve was obtained by measuring the overall characteristic curve 13 of the photovoltaic element 1 with complete illumination over its entire length, known as full flash. In the method according to the invention, the reference characteristic curve is reproduced with any positioning, and the deviation of the profiles of the two overall characteristic curves 13 obtained in comparison with the reference characteristic curve does not exceed 1% in any case. The method according to the invention is therefore largely independent of the positioning of the individual segments 5 when dividing the photovoltaic element 1.

[0096] 7 shows an exemplary embodiment of the influence of the length of the segments 5 when dividing the photovoltaic elements 1 in the method according to the invention. Identical and functionally equivalent elements are provided with the same reference numerals, and therefore reference is made to the above description in this regard.

[0097] The influence of the length of the individual segments 5, particularly the size of the individual segments 5, was investigated. According to the method of the present invention, the photovoltaic element 1 was divided into segments 5 having lengths of 10 cm, 20 cm, 30 cm, 60 cm and 2 m, and measurements were made.

[0098] Open circuit voltage V of photovoltaic element 1 oc and the fill factor FF were calculated from the final overall characteristic curve 13 as a function of the length of the segment 5. The obtained values ​​were compared with the overall characteristic curve of the photovoltaic element 1 obtained with full illumination over its entire length and the open circuit voltage V calculated therefrom. oc and compared with the fill factor FF. The deviation DV of the measurement result according to the invention compared with the complete illumination of the photovoltaic element 1 over its entire length oc and DFF are plotted in Figure 7. Open circuit voltage V oc is less than 1% for segment 5 lengths of at least 20 cm, and the fill factor deviation is less than 1.2% for segment 5 lengths of at least 20 cm. Individual segment 5 lengths of 10 cm may still show small deviations.

[0099] Segment 5, especially the area of ​​segment 5, cannot be made small at will, because for a segment 5 length of less than 10 cm, the deviation DV oc and DFF are significantly increased. The method according to the invention reproduces very well, for segments 5 of 20 cm or more in length, the values ​​obtained with full illumination of the photovoltaic element 1 over its entire length, and this is especially true for segments 5 of more than 60 cm in length.

Claims

1. A method of inspecting a photovoltaic element (1) to determine its performance and / or to identify defects therein, comprising: a) providing a photovoltaic element (1) having at least two photovoltaic cells connected in series with each other; b) providing a dark characteristic curve (3) of the photovoltaic element (1) at a specific voltage applied to the photovoltaic element (1); c) dividing the photovoltaic element (1) theoretically into a plurality of individual segments (5); d) measuring characteristic curves (7) of the plurality of individual segments (5) of the photovoltaic element (1) in a time sequence, wherein each of the at least two photovoltaic cells extends successively in a direction in which the plurality of individual segments (5) are successive, the individual segments (5) being illuminated by a lighting device (9) at the specific voltage applied to the photovoltaic element (1), the photovoltaic element (1) being moved along a direction of travel (11) relative to the lighting device (9) and / or the lighting device (9) being moved along a direction of travel (11) relative to the photovoltaic element (1); e) determining an overall characteristic curve (13) of the photovoltaic element (1) according to the dark characteristic curve (3) and the measured characteristic curves (7) of the individual segments (5), whereby the photovoltaic element (1) can be inspected; A method wherein in step c), each of said at least two photovoltaic cells is theoretically divided into said plurality of individual segments (5).

2. 2. The method according to claim 1, wherein the individual segments (5) are illuminated over an area (15) including the entire photoactive area thereof and / or the individual segments (5) of the photovoltaic elements (1) and / or the individual segments (5) themselves are each illuminated at least approximately uniformly.

3. 3. The method according to claim 1 or 2, wherein the overall characteristic curve (13) of the photovoltaic element (1) is determined in step e) by summing the photocurrents determined from the dark characteristic curve (3) of the photovoltaic element (1) and the measured characteristic curves (7) of the individual segments (5).

4. 4. The method according to claim 1, wherein the segments (5) of the photovoltaic element (1) have at least approximately no overlap with the previous segment (5) and / or the subsequent segment (5) in the direction of travel (11) and at least approximately no gaps, and / or the photovoltaic element (1) including the photoactive area is completely covered by the individual segments (5).

5. 5. The method according to claim 1, wherein the dark characteristic curve (3) of the photovoltaic element (1) is provided in step b) and / or is measured before or after step d) of the method, and / or steps c) and d) are performed together.

6. The method according to any one of claims 1 to 5, wherein the dark characteristic curve (3) of the photovoltaic element (1) in step b) is a dark characteristic curve (3) in complete or almost complete darkness.

7. 7. The method according to claim 1, wherein, if ambient light is present, at least one further characteristic curve (17) is measured at the specific voltage applied to the photovoltaic element (1) and in ambient light, the individual segments (5) and / or the photovoltaic element (1) are not illuminated by the lighting device (9), and the overall characteristic curve (13) of the photovoltaic element (1) is further ascertained in step e) as a function of the at least one further characteristic curve (17) in ambient light and / or the overall characteristic curve (13) of the photovoltaic element (1) is ascertained in step e) by further subtracting the ascertained ambient light photocurrent from the further measured characteristic curve (17) of the individual segments (5) in ambient light.

8. 8. The method according to claim 1, wherein the length of the segments (5) in the direction of travel (11) is between 10 cm and 10 m, and / or the photovoltaic elements (1) are divided into individual segments (5) according to the area (19) illuminated by the lighting device (9).

9. The method according to any one of claims 1 to 8, carried out in a roll-to-roll process and / or wherein the photovoltaic element (1) is a flexible photovoltaic element (1).

10. A photovoltaic element (1) that can be inspected using the method according to any one of claims 1 to 9.

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