DE102012017564B4 - Device for non-permanent electrical contacting of solar cells for measuring electrical properties - Google Patents

Abstract

Contacting device (1) for non-permanent electrical contacting of solar cells (3), wherein the contacting device (1) comprises:
a rigid support plate (5);
a plurality of electrical leads (7);
wherein the carrier plate (5) is optically transparent; and
wherein the electrical leads (7) are arranged to extend along a surface (10) of the carrier plate (5) from a central region (6) of the carrier plate (5) to an edge region (8) of the carrier plate (5) and via this surface (10 ) survive.

Description

FIELD OF THE INVENTION

The present invention relates to a contacting device for the non-permanent electrical contacting of solar cells and to their use for a measuring device for determining electrical properties, e.g. a current-voltage characteristic of a solar cell.

TECHNICAL BACKGROUND

Solar cells serve as photovoltaic elements to convert light into electricity. Light-generated charge carrier pairs, which have been spatially separated, for example, at a pn junction, must be supplied to an external circuit by means of electrical contacts of the solar cell. For this purpose, electrical contact arrangements must be provided both at the emitter and at the base of the solar cell.

In conventional solar cells, the emitter is usually arranged on a side of the solar cell facing the incident light. When generating an electrical contact arrangement on the front side of the solar cell, conflicting requirements must be taken into account. On the one hand, the contact arrangement should shade the front as little as possible, on the other hand, in particular a cross section of the contact arrangement should not be chosen too small in order to prevent excessive series resistance losses in deriving the current generated in the solar cell.

In order to meet these conflicting requirements, many conventional commercial solar cell contact arrangements are used in which a plurality of thin parallel contact tracks, which are also referred to as fingers and which are arranged at a distance of typically 0.5 mm to 3 mm to each other over the front of the solar cell are arranged distributed. In order to collect the current derived in the contact paths and forward it to adjacent solar cells, usually two or three wider busbars, which are also referred to as busbars used. This busbars preferably cross the narrow contact paths perpendicular, so that there is a so-called H pattern. Tinned copper strips can be soldered onto the wide busbars, which can be used to connect adjacent solar cells to form a string and ultimately to form a module.

However, in particular, the wide bus bars reflect a significant portion of the incident light, so that it is no longer a conversion into electricity available. It is therefore attempted to minimize the number of busbars. However, it has been observed that if the number of bus bars per solar cell area is too low, the efficiency of the solar cell may decrease despite reduced shadowing since generated electric current in the narrow contact paths has to travel long distances until it reaches a bus bar, so that series resistances within the contact tracks increase can result in significant series resistance losses.

Recent solar cell designs attempt to replace wide bus bars with a plurality, say five to thirty, of individual wires, each perpendicular to the fingers, and to solder the wires to each one of the fingers. In order to reduce an associated workload, the wires or electrical lines can be applied to thin films, which are then permanently connected to the solar cell. Such a concept is for example in the WO2007 / 071064 described. Similar solar cell concepts are also in the DE 603 17 805 T2 as in Braun et.al .: "Solar Cell Improvement by Using a Multi Busbar Design as Front Electrode", April 2012 , Elsevier LTD.selection, www.signsdirect.com. Such concepts promise, inter alia, due to an expected reduced recombination, reduced shading and reduced series resistances higher efficiencies in the solar module compared to conventional contact arrangements with H patterns.

In the production of solar cells, there is a certain dispersion with regard to the electrical properties of the solar cells produced. The electrical properties of each solar cell should be known as well as possible, for example, to be able to use the solar cells as best as possible in a solar module. So it may be necessary for best possible later interconnection in a solar module to divide the solar cells into power classes. For this purpose, usually a non-linear current-voltage characteristic of the solar cell, which is also referred to as I-V characteristic, recorded, which indicates how much power a solar cell generates when illuminated with a solar simulator at a given applied voltage. Further, for example, using electroluminescence measurements, internal problems of the solar cell, e.g. triggered by local shorts, are detected. In order to determine the electrical properties, it may be necessary in the context of industrial solar cell fabrication to temporarily terminate contacts of the solar cell, i. non-permanent, from the outside to contact electrically.

Such as in the US 2010/0045264 A1 described in a similar manner, in conventional solar cells with wide busbars lying on a metal holder with its back solar cell this contacted on its front side usually using spring-loaded contact pins, the contact pins are pressed onto the bus bars. In this way, a good electrical contact between the solar cell and a measuring arrangement can be produced in a simple and reproducible manner.

In particular, in the above-mentioned novel solar cell concepts without wide busbars, however, the problem may arise that for correct determination of the I-V characteristic of a solar cell every single finger would have to be contacted several times electrically. This can bring a considerable effort for the generation of many necessary contact points with it. In addition, care must be taken that in such a contact no excessive shading of the solar cell is effected. Furthermore, the contact points generated should be reversibly solvable, that is, the solar cell should be non-permanently contacted.

SUMMARY OF THE INVENTION

There may be a need for a contacting device that is suitable for non-permanent electrical contacting of solar cells, particularly in determining their electrical properties, and that, inter alia, prevents or at least reduces the above-mentioned problems and deficiencies of conventional contacting devices and methods can. In particular, there may be a need for a contacting device, by means of which a solar cell front side can be easily and reliably electrically contacted, wherein shading of the solar cell during measuring, for example, an I-V characteristic should be kept low. Furthermore, it may be advantageous if, in determining e.g. the I-V characteristic using the contacting device are both optical and electrical prevailing conditions similar to those prevailing in a solar cell receiving the solar cell.

Such a need can be met by means of a contacting device according to the main claim and by means of a measuring device and its use according to the independent claims. Advantageous embodiments of the contacting device are defined in the dependent claims.

According to a first aspect of the present invention, a contacting device is proposed which comprises a rigid support plate and a plurality of electrical leads. The carrier plate is optically transparent. The electrical lines are arranged to extend along a surface of the carrier plate from a central region of the carrier plate to an edge region of the carrier plate and project beyond this surface of the carrier plate.

According to a second aspect of the present invention, there is provided a measuring device for determining electrical characteristics such as e.g. proposed an I-V characteristic of a solar cell. The measuring device has a contacting device according to the first aspect of the present invention and a measuring device. The meter is designed to measure both a current flowing between two power terminals and a voltage applied between two power terminals. At least one of the electrical leads of the contacting device is connected at its ends in each case with voltage terminals of the measuring device. Several of the electrical leads of the contacting device are connected at their ends respectively to power terminals of the measuring device.

According to a third aspect of the present invention, the contacting device according to the first aspect of the invention is used in determining electrical characteristics such as e.g. used an I-V characteristic of a solar cell.

Ideas for the above-described aspects of the present invention may be considered, inter alia, as being based on the following observations and findings:

As described in the introduction, conventional solar cells for determining their electrical properties can be temporarily contacted with spring-loaded contact pins by pressing them onto the wide bus bars. In this case, the contact pins can usually be pressed with the help of over the busbars to be arranged bridges or alternatively only at the edge of the solar cell on the busbar tracks to keep shading by a holder holding the pins low.

Although such a determination of the electrical properties of a solar cell using spring-loaded contact pins can be carried out reliably and reproducibly, it often suffers from several deficits.

For example, the IV characteristic of a solar cell is usually determined in a state in which the bus bars of the solar cell are not yet soldered with copper bands. The unsoldered However, busbars have a much higher electrical resistance than is the case with the solar cells soldered in the module. On the one hand, due to the series resistances, there may be a loss of power during the dissipation of the current generated in the solar cell; on the other hand, the voltages dropping across such series resistors may result in different electrical potentials at different positions within the solar cell, which may influence the mode of operation of the solar cell. for example, by forming equalizing currents. Therefore, it can already be advantageous in the characterization of conventional solar cells not to derive the current generated by the solar cell exclusively at the edge of busbar tracks.

In novel solar cell concepts in which no busbars are provided, a tapping of the generated power using spring-loaded pins is usually not possible because the pins would have to contact a variety of very thin contact paths with a width of, for example, less than 150 microns. Even if it were assumed that very fine contact pins could contact such narrow contact paths, each contact pin would have to strike an assigned contact path exactly. In addition, it should also be prevented here that a device holding the contact pins leads to excessive shading of the solar cell. Contacting the solar cell exclusively at the outermost edge, however, leads to problems with regard to the series resistances occurring for the reasons described above, even more so than in the contacting of wide busbars.

In addition, it should be noted that e.g. In conventional methods for determining the I-V characteristic of a solar cell, the solar cell is characterized before it is encapsulated in a solar module. In this unencapsulated state, however, the solar cell is subject to different optical and electrical boundary conditions than in an encapsulated module.

By using the contacting device proposed here, e.g. On the one hand, an I-V characteristic of a solar cell can be reliably determined, on the other hand, the optical and / or electrical boundary conditions can prevail similarly, as is the case after encapsulation in a solar module.

In the proposed contacting device, the solar cell is no longer contacted by means of individual contact pins. Instead, a plurality of electrical lines are provided for such electrical contacting, which can be similar to a wire mesh placed over the front of the solar cell and there come into contact with the metal contacts of the solar cell. For example, at least 2, preferably between 5 and 30 electrical lines can be provided. In this way, an interconnection of the solar cell can be achieved, which corresponds for example in solar cells without busbar tracks of that interconnection, as it is realized in the finished solar module. In this case, the electrical lines can be provided in the form of bare metallic wires, so that an electrical contact is established in the case of a mechanical contact of the electrical lines with the metal contacts of the solar cells.

However, it could be observed that the bare wires of the wire mesh alone can not apply sufficient contact pressure to the solar cell due to their low weight, as a sufficient and reliable electrical contact would be guaranteed.

For this reason, a largely rigid, optically transparent carrier plate is arranged above the wire grid. The support plate should be sufficiently rigid that by pressing the support plate to the solar cell provided on the support plate electrical lines can be pressed with a substantially homogeneously distributed force to the surface of the solar cell and the metal contacts provided thereon. Accordingly, no thin film is suitable for the carrier plate, but the carrier plate should have at least a thickness of at least 0.5 mm, preferably at least 2 mm. For example, the support plate may have a similar thickness of between 5mm and 10mm, as used in the transparent cover plates typically used in solar panels.

In addition to its mechanical strength, the support plate should be as optically transparent as possible, that is, as much as possible of the incident light, for example a solar simulator should be transmitted through the support plate in order to be absorbed in the solar cell can. For this purpose, the support plate should, in particular in a predominant part of the optical spectral range, in which the solar cell can convert light into electricity, for example in silicon solar cells between 300 nm and 1200 nm wavelength, transmit as well as possible, that is, have as little absorption and reflection. For example, a transmittance of the support plate for use with silicon solar cells should be greater than 80%, preferably greater than 90%, at least in the range of 350 nm to 1150 nm.

The electrical lines can be directly on the carrier plate or at least with this be arranged mechanically connected. For example, the electrical wires may be glued to the carrier plate in the form of wires. Thus, the electrical leads can be precisely positioned on the solar cell surface using the easy-to-handle support plate while determining an IV characteristic. The fact that the electrical lines protrude beyond the surface of the support plate, it can be achieved that the electrical lines using the support plate can be pressed onto the surface of the solar cell and the metal contacts provided there and low contact resistance between the electrical due to the locally acting high pressure Lines of the contacting device on the one hand and the metal contacts of the solar cell on the other hand can be achieved. In addition, it can be avoided that the surface of the carrier plate comes directly into contact with the surface of the solar cell, which could at worst result in damage to the solar cell and / or scratching of the carrier plate.

Hereinafter, possible features and advantages of embodiments of the invention will be further described in detail.

Between the electrical lines and the carrier plate, an elastic material may be arranged. Because of this elastic material, the lines can on the one hand be firmly mechanically connected to the support plate and on the other hand, however, be reversibly resiliently displaced with respect to the support plate. When pressure is applied to the lines, they can be pressed into the elastic material, for example, so that, for example, height differences in the metal contacts of the solar cell to be contacted by the lines, as may result, for example, from manufacturing variations in thickness, can be compensated. For example, depending on the elasticity of the elastic material used and the thickness of the layer of such material interposed between the conduits and the support plate, local height differences of up to 30 μm, possibly even up to 100 μm, can typically occur in the manufacture of solar cell contacts using screen printing technologies occur, be balanced.

Any elastic materials such as elastic polymers, in particular silicone, can be used. If the elastic material is not stored exclusively in the area between the lines and the carrier plate, the elastic material used should be optically transparent in order to avoid shading losses.

In the support plate line-shaped, preferably rectilinear depressions may be provided, wherein the electrical lines may be partially received in these line-shaped depressions. The provision of such recesses may serve to precisely adjust the lines in relation to the carrier plate. The depressions can be subsequently introduced by means of any method, for example by sawing, lasers, etching, etc. in the carrier plate. Alternatively, the backing plate can be made directly, for example using a suitable mold, with the desired trench structure. The recesses should be dimensioned in this case in such a way that a line can be at least partially received in the recess. In the production of the contacting device thus the electrical leads can be inserted into the wells and fixed there, for example, adhesive. Alternatively, initially elastic material can be introduced into the depressions and then in each case an electrical line can be arranged above one of the depressions, so that the electrical line can be pressed under pressure into the depressions and the elastic material accommodated therein.

The line-shaped recesses may have flanks which extend at an oblique angle, that is, not at right angles, to the surface of the carrier plate. At such oblique flanks of the depressions, for example, from above perpendicularly incident on the support plate light can be reflected at an obtuse angle, so that this does not leave the support plate away from the underlying solar cell, but continues to run to the solar cell and ultimately absorbed in the solar cell can be. In this way, an effective optical width, that is to say a width with vanishing optical transmission, of the linear depressions and the electrical lines arranged in these can be optimized in a desired manner. In this case, it can be exploited that, due to the different refractive indices of the material of the carrier plate on the one hand and a material provided in the depressions on the other hand, total reflection or at least enhanced reflection at the flanks of the depressions can occur. Optionally, the flanks of the recesses can also be locally mirrored, for example by vapor deposition or chemical deposition of a metal layer. Depending on the choice of the geometry of the cross section of the recesses, an effective optical width of the recesses or the underlying electrical lines can be varied. In extreme cases, the electrical lines can even be "hidden".

As already indicated, the carrier plate should have the highest possible optical transmission. To minimize reflection losses on the carrier plate, antireflection layers can be provided on the surface of the carrier plate. In order to minimize absorption losses within the carrier plate, on the one hand the thickness of the carrier plate can be chosen as low as possible, but without reducing the mechanical strength of the carrier plate to a minimum. For example, the thickness of the backing plate should not be less than 0.5 mm. On the other hand, it is possible to use for the carrier plate materials having the lowest possible absorption coefficient in the region of the light spectrum to be transmitted. In particular, the support plate can be made of glass, with ordinary window glass having a sufficiently high transmission in the spectral range above 400 nm. In order to be able to achieve a high transmission in the spectral range below 400 nm, for example in the spectral range from 300 nm to 400 nm, special low-iron glasses which have a reduced iron content or borosilicate glasses can be used. Since low-iron glasses are also usually used as a cover layer in solar modules, it can be achieved by using a carrier plate made of low-iron glass that the light reaching the solar cell has a similar spectrum as solar cells receive it encapsulated in a module. Accordingly, very practical IV characteristics can be recorded. Alternatively, however, the carrier plate can also consist of other highly transparent materials such as transparent plastics such as PMP, LDPE, PP, PVC, PET, PC or PS. To increase the transmission, it is also possible for one or more antireflection layers to be applied to surfaces of the carrier plate.

The electrical leads may be provided in the contacting device such that ends of a plurality of the electrical leads are electrically connected to each other and each to one of two common power terminals of the contacting device. The power generated by the solar cell can be dissipated at a plurality of contact points between the electrical lines and the metal contacts provided on the solar cell via the plurality of electrical lines coupled to the power connections, which are routed as parallel and equidistant as possible along the carrier plate. Due to the large number of such contact points and the most homogeneous possible distribution of the contact points over the entire front side of the solar cell, it can be achieved that current within the solar cell and within the metal contacts must always travel only short distances before it can be dissipated in the contacting device. Accordingly, series resistances can be kept low and the current flow can be homogenized.

Between each of the lines and one of the power connections, a series resistor can be interposed in each case. The series resistor may have an electrical resistance of between 0.01 Ω and 100 Ω, preferably between 0.1 Ω and 10 Ω. The provision of such series resistors can lead to a homogenization of the current flow over various electrical lines of the contacting device. Without a homogenization caused by such series resistors, slight differences in the contact resistance between individual electrical leads and metal contacts contacted by them can lead to equalization currents within the solar cell and thus to a falsification of the measured IV characteristic due to the different contact resistances the current flowing through different voltages can fall locally. In order to minimize the influence of locally varying contact resistances and to achieve homogenization, the series resistors should have an electrical resistance which is significantly greater than the expected contact resistance.

While the majority of the electrical leads of the contacting device are to be used for current measurement in the determination of an I-V characteristic, at least one of the electrical leads can be used for a separate voltage measurement. In this way, similar to a conventional four-point measurement, it can be avoided that in determining an I-V characteristic, the voltage drops that occur in a current flow through contact and series resistors distort the measurement of the voltage generated by the solar cell. At least one of the electrical lines can therefore be electrically connected at each of its ends to one of two voltage terminals of the contacting device.

This at least one line used for voltage tapping may preferably be arranged near the center of the carrier plate. While the current during the determination of an I-V characteristic should be derived as homogeneously as possible on the entire surface of the solar cell, it may be sufficient to tap the voltage only at one position, wherein a tap of the voltage near the center of the solar cell appears advantageous.

The electrical line used for the voltage tap may, in contrast to the electrical lines used for the current tap, preferably be provided with an electrically insulating sheath, which leaves the electrical line only partially exposed. It can thereby be achieved that the voltage tapping line does not make contact with the solar cell at several positions both in the middle and near the edge of the solar cell, which could lead to distortions of the measured IV characteristic due to locally different series resistance losses and possible compensating currents.

It should be noted that in determining an I-V characteristic, the voltage is also applied at other positions, i. off-center, can be tapped. Furthermore, the tapping of the voltage with a separate electrical line can be dispensed with in the context of a 4-point measurement and instead the voltage at the electrical lines used for the current tapping can also be tapped, ie. a 2-point measurement is performed.

The contacting device may have, in addition to the carrier plate, a frame surrounding the carrier plate. This frame can serve, for example, to mechanically stabilize the carrier plate. In addition, the power and voltage connections to be contacted from the outside can be provided on the frame. While the backing plate itself may be made of a material that is difficult to handle, such as brittle glass, the frame may be made of easily machined material such as metal or plastic. When determining an I-V characteristic, the frame, due to its own weight, can press the carrier plate against the underlying solar cell with increased pressure. In addition, the frame can be used to press the carrier plate against the solar cell due to an additional force applied to the frame.

The contacting device can also have a holding plate, on which the solar cell to be measured can be arranged. In this case, a seal for hermetically sealing a space located between the holding plate and the carrier plate may be provided on the carrier plate, on a frame attached to the carrier plate and / or on the holding plate. In the closed by means of this seal space between the support plate and the support plate, a negative pressure can be generated by means of which the support plate can be pulled towards the support plate and thus to the arranged on the support plate solar cell and pressed against it. In addition, a negative pressure between the holding plate and the solar cell can be generated in order to fix the solar cell reliably on the holding plate. The holding plate may for example be part of a measuring table.

It should be noted that possible features and advantages of embodiments of the invention herein in part with reference to a contacting device according to the invention, partly with respect to a measuring device according to the invention for determining an IV characteristic of a solar cell and partly with respect to a use of a contacting device in determining a IV characteristic of a solar cell are described. A person skilled in the art will recognize that the features described can be suitably combined or exchanged with one another and in particular can also be transferred from the contacting device to the measuring device or its use or vice versa in order to arrive at further embodiments and possibly synergy effects.

list of figures

• 1 zeigt eine perspektivische Ansicht von unten einer erfindungsgemäßen Kontaktierungsvorrichtung.
• 2 zeigt eine perspektivische Ansicht von oben einer Messvorrichtung mit einer Kontaktierungsvorrichtung gemäß einer Ausführungsform der vorliegenden Erfindung.
• 3 zeigt eine teilweise Querschnittsansicht durch eine mit Leitungen versehene Trägerplatte einer erfindungsgemäßen Kontaktierungsvorrichtung.
• 4 (a)-(c) zeigen Querschnittsansichten von in einer Trägerplatte auszubildenden Vertiefungen mit unterschiedlicher Geometrie für eine erfindungsgemäße Kontaktierungsvorrichtung.

The above-described and other possible aspects, features and advantages of the invention will become apparent from the following description of specific embodiments with reference to the accompanying drawings, in which neither the description nor the drawings are to be construed as limiting the invention.

• 1 shows a perspective view from below of a contacting device according to the invention.
• 2 shows a perspective view from above of a measuring device with a contacting device according to an embodiment of the present invention.
• 3 shows a partial cross-sectional view through a ducted carrier plate of a contacting device according to the invention.
• 4 (a) - (c) show cross-sectional views of recesses to be formed in a carrier plate with different geometry for a contacting device according to the invention.

The figures are only schematic and not to scale. Like reference numerals designate the same or similar features in the figures.

Description of preferred embodiments of the invention

In the 1 to 3 is an embodiment of a contacting device 1 for non-permanent electrical contacting of a solar cell 3 shown. In 2 are additionally schematically components of a measuring device 45 represented by the contacting device 1 an IV characteristic of a solar cell 3 can determine.

The contacting device 1 has a rigid support plate 5 and a plurality of electrical wires 7 on. To the carrier plate 5 around is a frame 9 provided, which is the carrier plate 5 holds and with the support plate 5 hermetically sealed. The frame 9 can on a mounting plate 11 be arranged, on which also the solar cell 3 can be arranged. The frame 9 can do this on the retaining plate 11 using on the retaining plate 11 provided pin 13 and in the frame 9 provided corresponding positioning holes 17 be accurately positioned. Between the frame 9 and the retaining plate 11 is a seal 15 intended. Using a vacuum connection 19 serve through hole can in an interior of the contacting device 1 between the holding plate 11 and the carrier plate 5 a negative pressure can be applied to the carrier plate 5 towards the on the holding plate 11 arranged solar cell 3 sucks. At the same time, using a negative pressure, the solar cell 3 on the retaining plate 11 be fixed so that they can not slip during a Kontaktierungsphase.

In the example shown, the solar cell 3 Although thin metal contact fingers 21 on, which are straight and parallel to each other over the entire front of the solar cell 3 extend and have, for example, a finger width of about 100 microns and a distance between adjacent fingers of about 1.5 mm to 3 mm. The solar cell 3 but has no broad busbars.

To the busbar-less solar cell 3 to contact as homogeneous as possible, has the contacting device 1 on the carrier plate 5 a variety of electrical wires 7 in the form of straight wires. The wires 7 are essentially perpendicular to the contact fingers 21 the solar cell 3 , The wires 7 extend substantially parallel to each other and have a uniform distance from each other, wherein the distance may for example be between 0.3 cm and 2 cm, preferably about 1 cm. The wires 7 extend from a central area 6 the carrier plate 5 towards the edge areas 8th , which at both ends to the central area 6 and to the frame 9 adjoin.

As in 3 They are clearly visible in the carrier plate 5 several linear depressions 23 introduced in the form of straight trenches. Dimensions of the wells 23 , in particular their width, are chosen to be larger than dimensions, ie the diameter of the electrical lines 7 , It is noted in this regard that in particular neither the dimensions of the wells 23 and the electrical wires 7 nor the distance between adjacent wells 23 is shown to scale in the figures.

The wells 23 are mostly with an elastic material 25 such as silicone filled. In this elastic material 25 are the wires 7 partially inserted and in this way firmly with the carrier plate 5 connected. The wires 7 protrude outward over a surface 10 the carrier plate 5 above. At a pressure on the lines 7 how it can arise when the wires 7 in contact with the solar cell 3 and the contact fingers arranged thereon 21 come, can the wires 7 resilient in the elastic material 25 be pressed. In this way, for example, local height differences on the solar cell 3 , at the contact fingers 21 and / or at the lines 7 be compensated. In addition, a flexible bracket of the frame 9 allow a possible wedge shape of a solar cell 3 or the holding plate 11 compensate.

As in the 4 (a) - (c) exemplified, the depressions 23 have different cross-sectional geometries.

At the in 4 (a) example shown has the recess 23 a rectangular cross section. From above irradiated light 27 can do this at an interface 29 between the material of the carrier plate 5 and the possibly filled with elastic material inside the recess 23 be reflected. Because of such reflection and because of the for the lines 7 used opaque wire may thus result in partial shading of the solar cell 3 around the electrical wires 7 come when, for example, when measuring an IV characteristic from above with a solar simulator with light 27 is illuminated.

As in the 4 (b) and (c) may have lateral edges 31 the wells 23 but not like in 4 (a) perpendicular but at an oblique angle to the surface of the support plate 5 be aligned. On these sloping flanks 31 can radiate light from above 27 be reflected at an obtuse angle, so it does not like in 4 (a) back up from the carrier plate 5 out but obliquely downward toward the solar cell 3 is reflected.

Alternatively, the wells can 7 also other than those in the 4 (a) to (c) shown geometries. For example, the depressions can be circular-arc-shaped and thus the contour in the cross-section of circular electrical lines 7 be adjusted. The electrical lines themselves can have different cross-sectional geometries, for example circular, oval, triangular, rectangular, etc.

How strong and in which direction the incident light 27 towards the solar cell 3 is reflected, depends both on the geometry of the depression 23 and the electric wire 7 as well as the refractive indices of the support plate 5 and in their depressions 23 intended materials from. If necessary, the flanks 31 be mirrored.

By suitable choice of the geometry of the wells 23 and the materials used can be the effective optical width of the pits 23 and optionally the underlying electrical lines 7 be optimized. As a result, for example, the optical conditions as they are after encapsulation of the solar cell 3 prevail in a module, be reproduced as accurately as possible. In the in 4 (c) illustrated extreme case of a pointed triangular depression 23 can the electric wire 7 even optically "hidden".

As in 1 To recognize well, extend the electrical wires 7 along the entire longitudinal direction of the carrier plate 5 and are at both ends 33 . 35 with substrates 37 connected in the frame 9 are admitted. About these substrates 37 are most of the electrical wires 7 with each other and each with externally contactable common power connections 55 the contacting device 1 (schematically in 2 shown) electrically connected. These electrical lines are thus connected in parallel and serve during the determination of an IV characteristic for tapping the in the solar cell 3 generated electricity.

To the through the different electrical wires 7 flowing current flow for the entire contacting device 1 to homogenize, are the leads 7 at their ends with in the substrate 37 provided resistors 39 connected. The wires 7 extend to both opposite areas of the frame and series resistors 39 are at both longitudinal ends of the carrier substrate 5 provided so that the of the solar cell 3 generated electricity can be tapped on both sides, thereby increasing the effective length of the electrical wires 7 to half the real length of these lines 7 shorten, so that a lower series resistance of the lines 7 is effected. Alternatively, the wires could 7 also only on one side of the carrier plate 5 to power connections 55 be guided and looped through on the opposite side.

A single, in the middle of the support plate 5 arranged electrical line 47 Although runs parallel to the other electrical lines 7 but is not electrically shorted to them. This line 47 can for a tapping on the solar cell 3 applied voltage can be used. Since at most a very small electric current flows through it, voltage drops due to, for example, contact resistances or series resistances can be neglected. The administration 47 can be realized as isolated, for example, paint-insulated thin wire with negligible shading, so that the voltage of the solar cell 3 only picked up where the paint was removed locally. Thus, a voltage tap at any position of the solar cell, preferably as centrally as possible within the solar cell, is possible.

To an IV characteristic of a solar cell 3 using the contacting device 1 to be able to determine at least one provided for the voltage tap electrical line 47 via voltage connections 57 the contacting device 1 with voltage connections 51 a measuring device 49 and the several provided for the power tap electrical lines 7 with power connections 53 of the meter 49 electrically connected, as shown schematically in 2 is shown.

The contacting device described 1 and their use in determining an IV characteristic of a solar cell using a suitably equipped measuring device 45 can be the measurement of electrical characteristics of the solar cell 3 under the same electrical conditions as exist in the finished solar module, and allow similar optical conditions. This allows a more accurate classification of the solar cells and thus lower mismatch losses in solar modules.

Finally, it should be noted that the terms "comprise", "exhibit" etc. are not intended to exclude the presence of additional elements. The term "a" does not exclude the presence of a plurality of elements or objects.

LIST OF REFERENCE NUMBERS

1

contacting

3

solar cell

5

support plate

6

Central area

7

electrical line

8th

border area

9

frame

10

Surface of the carrier plate

11

Retaining plate

13

spigot

15

poetry

17

positioning holes

19

Vacuum port

21

contact fingers

23

Depressions in carrier plate

25

elastic material

27

incident light

29

Interface support plate / recess

31

oblique flank of a depression

33

cable ends

35

cable ends

37

substratum

39

resistors

45

measuring device

47

electrical cable for voltage tap

49

gauge

51

Voltage connections of the meter

53

Power connections of the meter

55

Power connections of the contacting device

57

Voltage connections of the contacting device

Claims (15)

Contacting device (1) for non-permanent electrical contacting of solar cells (3), wherein the contacting device (1) comprises: a rigid support plate (5); a plurality of electrical leads (7); wherein the carrier plate (5) is optically transparent; and wherein the electrical leads (7) are arranged to extend along a surface (10) of the carrier plate (5) from a central region (6) of the carrier plate (5) to an edge region (8) of the carrier plate (5) and via this surface (10 ) survive. Contacting device according to Claim 1 , wherein between the electrical lines (7) and the carrier plate (5) an elastic material (25) is arranged. Contacting device according to one of Claims 1 or 2 , wherein in the support plate (5) line-shaped recesses (23) are provided whose cross-section is dimensioned such that the electrical lines (7) in the line-shaped recesses (23) can be at least partially accommodated. Contacting device according to Claim 3 wherein the line-shaped recesses (23) have flanks (31) which extend at an oblique angle to the surface (10) of the carrier plate (5). Contacting device according to one of Claims 1 to 4 , wherein the support plate (5) consists of glass, in particular of low-iron glass or borosilicate glass. Contacting device according to one of Claims 1 to 5 , wherein the electrical lines (7) are arranged parallel and equidistant from each other. Contacting device according to one of Claims 1 to 6 in that ends (33, 35) of a plurality of the electrical lines (7) are electrically connected to each other and each to one of two common power terminals (55) of the contacting device (1). Contacting device according to Claim 7 , wherein between each of the lines (7) and one of the power terminals (55) in each case a series resistor (39) with an electrical resistance of between 0.01 and 100 ohms is interposed. Contacting device according to one of Claims 1 to 8th in which at least one electrical line (47) is electrically connected at each of its ends to one of two voltage terminals (57) of the contacting device (1). Contacting device according to Claim 9 wherein the at least one electrical line (47) is disposed near the center of the carrier plate (5). Contacting device according to Claim 9 or 10 , wherein the at least one electrical line (47) is partially covered by an electrical insulation and partially exposed. Contacting device according to one of Claims 1 to 11 , further comprising a frame (9) surrounding the support plate (5). Contacting device according to one of Claims 1 to 12 , further comprising a holding plate (11) on which the solar cell (3) is to be arranged, and a seal (15) for hermetically sealing a space between the holding plate (11) and the carrier plate (5). Measuring device (45) for determining an IV characteristic of a solar cell, wherein the measuring device (45) comprises: a contacting device (1) according to one of Claims 1 to 13 ; a measuring device (49) which is designed to both a current flowing between two power terminals (53) of the measuring device (49) and current measure a voltage between two voltage terminals (51) of the meter (49); wherein at least one of the electrical leads (47) of the contacting device (1) is connected to the voltage terminals (51) of the measuring device (49) and wherein a plurality of the electrical leads (7) of the contacting device (1) are respectively connected to the current terminals (51) of the Measuring device (49) are connected. Use of a contacting device (1) according to one of Claims 1 to 13 in determining electrical properties of a solar cell (3).

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