DE102012015439A1 - Method and device for laminating objects, in particular solar cells - Google Patents

Abstract

A method and a device (1) are proposed for laminating objects to be encapsulated, in particular solar cells (15) to form solar modules (3). In a housing (5) of a laminator, the solar cells (15) can be embedded in EVA (ethylene vinyl acetate) and heated to over 120 ° C on a heating plate (9), whereby they are generated by generating a negative pressure with the aid of a pressure membrane (19) are pressed together. UV light (31) coming from a lighting device (29) is directed onto the EVA (13) through an opening (25). It was observed that fluorescence-active centers (43) arise during the crosslinking of the EVA, which centers can be excited with the aid of this UV light (31). Fluorescent light (45) emitted thereupon can be recognized by a detection device (37) and used when deriving information about a crosslinking state of the EVA. In order to make the method insensitive to a local reflectance of a sample, the reflectance can also be measured with an additional light source that emits light in the fluorescence range of the EVA and used to calibrate the fluorescence measurement results. In this way, the state of networking of the EVA can be determined in-situ or, alternatively, determined after the solar module (3) has been completed.

Description

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for lamination of articles to be encapsulated. More particularly, the invention relates to a method and apparatus for laminating solar cells to produce encapsulated solar modules.

TECHNICAL BACKGROUND

Items such as electrical components are often encapsulated to protect them from environmental influences. For example, the objects should be protected against mechanical damage or moisture to prevent corrosion. For this purpose, the objects are often embedded in plastic. To produce the encapsulation, suitable plastic material can be arranged around the object to be encapsulated. The plastic material can be provided for example in the form of plastic films, plastic powder or plastic granules. The plastic material can then be liquefied, for example, by heating beyond a liquefaction temperature, so that the plastic material can fill any cavities and then during solidification the objects to be encapsulated can fit tightly and tightly.

Hereinafter, the lamination of objects to be encapsulated will be explained mainly by the example of lamination of solar cells to be encapsulated to thereby produce encapsulated solar modules. It should be noted, however, that embodiments of the method according to the invention or of the device according to the invention can also be used for lamination of other objects to be encapsulated.

Further, as an example of a material used for laminating the articles, EVA (ethylene-vinyl acetate) is always used. It is pointed out, however, that embodiments of the method according to the invention or of the device according to the invention can also be used for lamination with other crosslinking polymer materials, provided that their fluorescence properties change during crosslinking.

To produce a solar module, a plurality of solar cells are first connected to one another by electrical connectors in order to interconnect them, for example, in series or in parallel. Subsequently, the solar cells are encapsulated to protect, for example, the brittle solar cells from mechanical influences, to protect the solar cells and their electrical connections from moisture and thus from corrosion and to be able to handle and fasten them easily. For this purpose, the solar cells are usually embedded in a transparent plastic layer, for example made of EVA or silicone rubber. For further improved protection, the solar cells embedded in this way are usually temporarily stored between a glass pane on the front side and a back side lining and the entire module is surrounded by a sturdy frame.

To produce the solar module, for example, an EVA film is arranged on a provided, cleaned glass pane and the solar cells connected to strings are placed on this film. After possibly further system components inserted and the solar cells were covered with another EVA film, the entire assembly is pressed together, for example, in a vacuum device such as a vacuum-drawing laminator or autoclave and heated to, for example, above 120 ° C. The initially milky EVA film is temporarily melted, whereby the EVA becomes crystal clear and three-dimensionally cross-linked, so that after the subsequent cooling a permanent composite in the form of a laminate between the solar cells, the surrounding EVA and other components such as the glass or the back side lamination arises. The aim is that the EVA crosslinks as completely as possible in order to achieve the highest possible mechanical stability, to use up as much as possible of reactive crosslinking components and, for example, to minimize the risk of delamination.

Since, in the manufacture of solar modules, the process of laminating the individual components to an encapsulated module represents the longest lasting single production step due to the relatively slow advancing crosslinking of the EVA, it may be desirable to control the crosslinking state or degree of crosslinking during the EVA the lamination process or after its completion know as accurately as possible or at least be able to estimate. In addition, it may be important to know the homogeneity of the crosslinking reaction on a solar module, because z. B. uneven heating of the module in the laminator z. B. can lead to uneven crosslinking reaction by bulging the glass during heating.

There are several methods to determine the degree of crosslinking of the EVA after completion of the lamination process. For example, in dynamic mechanical analysis (DMA), a sample of material is made from the Module removed and analyzed. However, this is a destructive method. Further measurement methods have been developed in which information about the degree of crosslinking can be determined or estimated using electrical measurements, mechanical measurements, thermal measurements or spectroscopic measurements.

However, all of these methods have disadvantages that do not make them suitable for use in laminating articles to be encapsulated in industrial manufacturing. For example, mechanical methods are generally non-destructive and do not allow instantaneous information about the degree of crosslinking of the EVA to be laminated. To carry out electrical measuring methods, additional electrode arrangements generally have to be provided, which can entail increased expense and increased costs. Thermal and spectroscopic measurement methods have hitherto been mostly complicated and / or unreliable.

SUMMARY OF THE INVENTION

There may be a need for a method and apparatus for lamination of articles to be encapsulated which, in particular, at least partially alleviates the aforementioned disadvantages of conventional methods. In particular, there may be a need for such a method or apparatus which can provide information about a crosslinking condition of a crosslinkable polymeric material used for lamination, such as e.g. B. EVA simple, inexpensive, reliable and / or preferably directly during the lamination process or shortly after completion of the same can be determined.

To meet such a need, the method and apparatus according to the independent claims of the present application are proposed. Advantageous embodiments are defined in the dependent claims.

According to a first aspect of the present invention, a method is proposed for laminating objects to be encapsulated, in particular solar cells, which comprises at least the following method steps: (a) embedding the objects to be encapsulated in crosslinkable polymer material, such as e.g. B. EVA (ethylene vinyl acetate); (b) pressing the articles embedded in the crosslinkable polymeric material; (c) heating the crosslinkable polymer material above 120 ° C, preferably at a temperature between 120 ° C and 200 ° C, and more preferably at a temperature between 130 ° C and 170 ° C; (d) illuminating the crosslinkable polymer material with light in an emission range of 320 nm to 400 nm, preferably 340 to 380 nm; (e) detecting fluorescent light from the illuminated crosslinkable polymer material having a wavelength in an absorption range of 400 nm to 600 nm, preferably 450 nm to 500 nm; and (f) deriving information about a crosslinking state of the crosslinkable polymer material based on the detected fluorescent light. The process steps (d) to (f) should be carried out during or after the heating of the crosslinkable polymer material to more than 120 ° C, that is, during or after step (c). The process steps described may, but need not necessarily, be carried out in the order given. For example, steps (b) and (c) may be performed in reverse order or simultaneously.

According to a second aspect of the present invention, an apparatus for lamination of objects to be encapsulated, in particular of solar cells, is proposed, wherein the apparatus has at least one lamination device and one monitoring device. The lamination device in this case has a pressing device for pressing the articles during or after they are embedded in crosslinkable polymer material, and a heating device for heating the crosslinkable polymer material surrounding the embedded articles to a temperature of over 120 °. The monitoring device has a lighting device for illuminating the crosslinkable polymer material surrounding the articles with light having a wavelength in an emission range from 320 nm to 400 nm and a detection device for detecting fluorescent light having a wavelength in an absorption range from 400 nm to 600 nm from the illuminated crosslinkable Polymer material to detect. The illumination device and the detection device are thus designed to perform fluorescence measurements. The monitoring device furthermore has an evaluation device in order to determine information about a crosslinking state of the crosslinkable polymer material on the basis of the detected fluorescent light. The proposed device can be designed to perform a method according to embodiments of the method described above according to the first aspect of the invention.

According to a third aspect of the present invention, there is provided an apparatus for determining information about a crosslinked state of crosslinkable polymer material. The device has two illumination devices, a detection device and an evaluation device. A first illumination device is adapted to the first-light-crosslinkable polymer material having a wavelength in one first emission range of 320 nm to 400 nm to illuminate. The second illumination device is adapted to irradiate the crosslinkable polymer material with second light having a wavelength in a second emission range of over 400 nm to e.g. B. 600 nm to illuminate. The detection device is designed to detect the fluorescent light caused by the first light and the reflected light caused by the second light, each having wavelengths in an absorption range of more than 400 nm. The evaluation device is adapted to determine information about a crosslinking state of the crosslinkable polymer material based on both the detected fluorescent light and on the basis of the detected reflected light.

A basic idea of the aspects of the present invention may be considered as based on the following finding: It has been found that a crosslinking state or degree of crosslinking of the crosslinkable polymer material used during lamination, especially when using EVA, during the lamination process in the changed elevated temperature of about 120 ° C, wherein the degree of crosslinking increases with increasing process time. The inventors have recognized that the change in the crosslinking state of the crosslinkable polymer material is accompanied by a change in the fluorescence properties of the EVA. With increased degree of crosslinking, increased fluorescence radiation was also observed. It is therefore proposed to use the observed correlation between the fluorescence properties and the crosslinking state of the crosslinkable polymer material in order to be able to determine the crosslinking state of the crosslinkable polymer material used during lamination in a simple, nondestructive, optical manner. A monitoring device used for this purpose can determine fluorescence properties of the partially or completely crosslinked crosslinkable polymer material with the aid of the illumination and detection device provided therein, for example directly during the lamination process, or alternatively shortly after completion of the lamination process Fluorescence properties allow deriving information about the crosslinking state of the crosslinkable polymer material.

In the following, possible features and advantages of embodiments of the method according to the invention or the device according to the invention will be described in further detail. In each case, EVA is described as an exemplary crosslinkable polymer material, representative of other crosslinkable polymer materials.

As a first method step, the objects to be encapsulated, that is, for example, the solar cells to be encapsulated, are embedded in EVA. In this case, the EVA can be provided for example in the form of films, as a powder or as granules and be arranged so that it surrounds the objects to be encapsulated as completely as possible.

Subsequently, the objects are pressed with the surrounding EVA, that is, it is exerted a pressure on the objects surrounding EVA and possibly simultaneously generates a vacuum in the pressure chamber. In this compressed state, the EVA is then heated to an elevated temperature of over 120 ° C. The EVA liquefies and penetrates into previously existing cavities and pores and fills them, so that the EVA after a subsequent cooling and solidifying the embedded objects completely and clearly transparent surrounds.

EVA is an elastomer, that is, a polymer that irreversibly cross-links under heat. During the heating of the EVA to more than 120 ° C, the EVA is progressively crosslinked with increasing heating time. An ultimate degree of cross-linking after encapsulation of articles may be highly relevant to later functionality of the EVA. For example, insufficient crosslinking can lead to delamination and corrosion in a solar module and affect mechanical stiffness of the EVA. To achieve complete crosslinking, the EVA should be heated as long as possible and at the highest possible temperatures during lamination. On the other hand, since heating of the EVA entails a considerable expenditure of energy and an extension of the lamination process results in increased production costs or a reduced production throughput, on the other hand the aim is to keep the heating of the EVA as short as possible and to limit it to the lowest possible temperatures.

The determination of the fluorescent properties of the EVA proposed herein by illuminating the EVA with UV light and measuring the resulting fluorescent light enables nondestructive, fast and reliable information on the degree of crosslinking of the EVA to be obtained during or after completion of the crosslinking process. Here, the knowledge is used that change the fluorescence properties of the EVA with progressive networking, so that there is an increasingly strong emission of fluorescent light.

It is believed that upon crosslinking the EVA, chromophores, that is, optically active centers, are formed which interact with each other UV light of a wavelength range of 370 nm ± 30 nm excite and then emit fluorescent light in a higher wavelength range above 400 nm.

In particular, it has been observed that the change in the fluorescence properties of the EVA appears to occur only when the process of compressing and heating the EVA under oxygen deficiency is performed. It is believed that oxygen inhibits or prevents the formation of chromophores or destroys the chromophores after a short time, so that in a non-oxygen deficient lamination process, there is no observable change in the EVA's fluorescence properties and thus no indication available for the current state of networking of the EVA. By "oxygen deficiency", it may be understood herein as meaning a significant reduction in the amount of oxygen in the ambient atmosphere during compression and heating, for example to less than 0.1%, preferably less than 0.001%, of the amount of oxygen present under normal ambient conditions. For example, to achieve the desired oxygen deficiency, the articles may be vacuum pressed and heated, as is often the case in conventional laminators.

In order to be able to determine the fluorescence properties of the EVA, it is illuminated with UV light which at least also contains light of a spectral range of between 320 nm and 400 nm. Although it is not excluded that the exciting light also includes spectral regions with less than 320 nm, it is assumed that short-wave UV light of significantly less than 340 nm is generally not transmitted through a glass plate, as they usually together with the EVA is used to encapsulate objects, particularly solar cells, so that shortwave UV light does not reach the EVA. On the other hand, the stimulating light should as far as possible include no spectral ranges above 400 nm, since in this spectral range the fluorescent light is emitted and a reflection or backscattering of irradiated excitation light in the same spectral range would thus make the measurement of the fluorescent light more difficult.

In order to illuminate the EVA with UV light, the illumination device may comprise a simple, inexpensive LED or a laser diode or any other UV light source. By way of example, the detection device can be a photodiode which is sensitive in the specified spectral range.

In particular, the detection device can be designed to measure the intensity of fluorescent light which is emitted over an entire spectral range of, for example, 400 to 600 nm, and output it as a total signal. In other words, the detection device need not be designed to be able to analyze the fluorescent light toward its spectral intensity distribution, but it is sufficient to determine a total intensity of the fluorescent light. Therefore, very simple and thus inexpensive photodetectors can be used for the detection device.

On the basis of the detected fluorescent light, information about a current state of crosslinking of the EVA can be derived. The fluorescence light measurements can be carried out repeatedly during the lamination process, that is to say during the heating of the EVA to more than 120 ° C., and monitored virtually continuously as the fluorescence properties of the EVA change.

Signals of an evaluation device, which determines the information about the crosslinking state of the EVA on the basis of the detected fluorescent light, can be used to control the lamination device or, in particular, the heating device used therein. In particular, the heating of the EVA caused by the heater may be terminated above 120 ° C after an intensity of detected fluorescent light exceeds a predefined threshold.

In other words, the lamination device can promote the lamination process by continuously compressing and heating the EVA surrounding the articles to be encapsulated, thereby causing increasing cross-linking of the EVA, the monitoring device repeatedly determining the fluorescence properties of the EVA in-situ and driving the lamination device to the lamination process cancel as soon as the intensity of the detected fluorescent light has assumed a value in which it can be assumed, for example on the basis of previous experimental investigations, that adequate crosslinking of the EVA has been achieved.

Alternatively, information on the crosslinking state of the EVA can also be carried out only after completion of the lamination process by determining the then prevailing fluorescence properties of the EVA, for example, to be able to retrospectively check the degree of crosslinking of the EVA and, if appropriate, sort out or post-treat insufficiently crosslinked laminates. For this purpose, the process steps of lighting with stimulating UV light, Detecting fluorescent light and deriving the information on the state of crosslinking as possible within a period of one week after stopping the heating of the EVA, and in particular before the EVA is exposed to sunlight. This is based on the observation that the chromophores formed upon heating of the EVA and responsible for the changed fluorescence properties do not appear to be stable over time and, in particular when stored under oxygen supply, a reduction in fluorescence emissions can occur over time. Irradiation with sunlight can promote or accelerate this process. Reliable information about the crosslinking state of the EVA achieved during lamination can therefore only be derived within a relatively short period of time after the conclusion of the lamination process. In oxygen-tight encapsulated solar modules, z. Example, in a composite with a glass front and an aluminum backsheet or a glass back also significantly longer times (many months) can be used after lamination, as long as the module is not exposed to solar radiation or other similar strong UV light sources.

In the measurement of the fluorescence properties of the EVA, it is frequently to be assumed that, in addition to the fluorescent light to be measured, a portion of the light irradiated by the illumination device in the form of reflected or backscattered light is also likely to reach the detection device. Furthermore, it can be assumed that fluorescence light is generally emitted isotropically, with part of the fluorescence light being radiated directly towards the detection device and another part being emitted, for example, reflected towards the objects to be encapsulated and ultimately reaching the detection device at least partially. It is thus assumed that the light intensity measured by the detection device depends, inter alia, strongly on the reflection and scattering properties of the objects to be encapsulated and of the surrounding EVA. For example, it is to be expected that in the case of a solar module more stray light is generated via a metallic connector than via a central area of a solar cell provided with an antireflection coating, at which almost no fluorescent light is reflected. In order to minimize the influence of the measuring site on the determination of the degree of crosslinking of the EVA, two possible measures are proposed.

First, just before or at the beginning of the heating of the EVA, an initial intensity I ₀ of fluorescent light may be measured and then, at a later time during or after the heating, a current intensity I _t of fluorescent light measured. The current fluorescence light intensity can be normalized with the aid of the initial intensity, since it can be assumed that no or a negligible amount of fluorescence radiation occurs before or at the beginning of the heating due to the chromophores formed during the crosslinking of the EVA. A light scattering of the excitation light in the detector can be used as a measure of local scattered light. The information about a current state of crosslinking of the EVA can thus be derived from the current intensity and the initial intensity of measured fluorescent light on the basis of a quotient I _t / I ₀ . This quotient is largely independent of the reflectance at the measurement location and can thus serve as a robust parameter for determining the information about the crosslinking state of the EVA.

As a second alternative, in a device which is suitable for determining the fluorescence properties of the EVA and accordingly has a UV illumination device and a detection device for detecting the visible fluorescent light, an additional second illumination device can be provided. This can illuminate the EVA in the same spatial area as the first illumination device, but emit light that corresponds to the spectral range of the fluorescence of the EVA. While the light of the first illumination device can not be detected directly by the detection device because of its short wavelength, since it is not sensitive in this short-wave spectral range or is protected by filters, the light of the second illumination device can be directly reflected in the case of back reflection or backscatter to the detection device be detected by the detection device. Reflection and scattering properties of the objects to be encapsulated and of the surrounding EVA can thus be measured with the aid of the second illumination device and the detection device sensitive in the same spectral range. These measured optical properties can be used to calibrate the intensity of fluorescent light, which is preferably measured in a separate measurement process. The size which is preferably used to determine the degree of crosslinking is in this case the ratio between the measured fluorescence intensity and the reflection intensity measured at the same location.

In order to further increase the reliability of the measurement method, the lighting of the EVA may be performed periodically, wherein the lighting device may be turned on and off at a frequency of 1 kHz, for example, and the fluorescent light intensity may be detected by a lock-in method.

In one embodiment of the device according to the invention, the heating device may be formed with a heating plate. The pressing device may in this case be arranged on one side of the heating plate, whereas the lighting device and the detection device are arranged on an opposite side of the heating plate. In this case, the heating plate has an opening, for example in the form of a through-hole, through which the illumination device can illuminate the EVA surrounding the objects received in the pressing device and can reach the detection device through the fluorescent light.

In other words, a conventional laminator, as used for example for encapsulating solar modules, only needs to be slightly modified in order to make it suitable for carrying out the method according to the invention described above. In such a laminator, a hot plate is often used together with a vacuum pressing device to pressurize and simultaneously heat the objects to be encapsulated together with the surrounding EVA. It is now proposed to provide an opening in the otherwise opaque heating plate. Through this opening, the fluorescence properties of the heated EVA can be repeatedly measured during the lamination process and conclusions about the degree of crosslinking of the EVA can be drawn. The opening can be kept sufficiently small, so that no significant effect on the heating effect of the heating plate is formed by them. In addition, the opening or the lighting and detection devices attached thereto can be suitably sealed in order to avoid that there is a venting of the arranged on the opposite side of the heating plate pressing device and thus the loss of any prevailing vacuum there.

According to a further embodiment of a device according to the invention, the illumination device is designed and arranged such that light emanating from the illumination device strikes a surface of the EVA surrounding the objects at a substantially different angle than 90 °. Preferably, the illumination device directs a light beam onto the surface of the EVA in such a way, for example at an angle of 60 to 88 °, that reflected light does not strike the detection device which is usually arranged in the vicinity of the illumination device. In this way, a strong influence or even falsification of the measurement of the fluorescent light by directly reflected back excitation light can be avoided.

In a further embodiment of a device according to the invention, a first filter is arranged in a beam path between the illumination device and the lamination device, which filters out light having a wavelength above a cut-off wavelength of, for example, 400 nm, and a second path is present in a beam path between the lamination device and the detection device Filter arranged that filters out light with a wavelength below this cut-off wavelength. The cut-off wavelength of both filters can deviate by up to 50 nm from the 400 nm as long as the cut-off wavelength of both filters is matched.

In other words, the light directed by the illumination device onto the EVA should be freed as far as possible, for example by more than 80%, from spectral components above the cut-off wavelength with the aid of the first filter, whereas light received from that recorded in the lamination device EVA and the objects embedded therein to the detection device is irradiated, with the help of the second filter as far as possible to be freed from spectral components of less than the cut-off wavelength. It can thus be achieved that with the aid of the illumination device, although the fluorescence-active centers of the EVA can be excited, any reflected or backscattered light can not be detected by the detection device. With the aid of the additionally provided filters can be compensated that a lighting device, in particular a low-cost lighting device, hardly emitted only in a very narrow spectral range and thus could be ensured that no light would be emitted from it in the spectral range covered by the detection device. On the other hand, particularly cost-effective detection devices without an upstream filter can hardly be designed to perceive exclusively light in a spectral range above a detection limit, so that partially backscattered excitation light would be detected without the second filter.

While in the preceding description mainly the process steps essential for embodiments of the method according to the invention or the components essential for embodiments of the inventive device and their features have been described, a person skilled in the art recognizes that when laminating articles to be encapsulated, further process steps can be performed or be necessary can and may be provided or necessary in a laminating other components. In addition, a person skilled in the art will recognize that those described for embodiments of the method according to the invention Transfer features in an analogous manner to embodiments of the device according to the invention and vice versa. In particular, the described process and / or device features can be advantageously combined to arrive at further embodiments of the invention and possibly synergy effects.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent to those skilled in the art from the following description of exemplary 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 an apparatus for laminating to be encapsulated solar cells according to an embodiment of the present invention.

2 shows an enlargement of the in 1 dashed marked area.

3 shows a spectral intensity distribution of fluorescent light at various stages of a lamination process.

4 shows a graph illustrating the degree of crosslinking of EVA as a function of the heating time.

5 shows an apparatus for determining information about a degree of crosslinking of EVA in a finished laminated solar module according to another embodiment of the present invention.

The figures are only schematic and not to scale. The same reference numerals in the various figures refer to the same or equivalent features.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

1 shows a rough sectional view of a device according to the invention 1 for laminating solar cells in a solar module 3 , 2 shows an enlarged, more detailed sectional view of the in 1 dashed framed area of the device according to the invention 1 ,

The device 1 has a lamination device 2 with a pressing device 20 and a heater 10 on. The lamination device 2 has a two-part housing 5 on that along a separation edge 7 is hinged. Inside the case 5 is a heating plate in a lower area 9 as part of the heater 10 intended. On this hot plate 9 For example, the components to be encapsulated as a stack of a front glass pane 11 , one or more layers of EVA film 13 and solar cells embedded therein 15 and a backside lamination 17 to be ordered. Above this stack leading to the solar panel 3 is encapsulated, runs a pressure membrane 19 which is the lower area where the heating plate 9 and the components of the solar module 3 are arranged, gas-tight from an overlying area in the interior of the housing 5 separates. With the help of a vacuum pump 21 can thus be generated in the lower region, a negative pressure relative to the upper region, whereby by means of the pressure membrane 19 the components 11 . 13 . 15 . 17 of the solar module 3 pressed together and against the hot plate 9 be pressed. The pressure membrane 19 and the vacuum pump 21 are part of the pressing device 20 , Both the vacuum pump 21 as well as the heating plate 9 be doing this by a controller 23 controlled.

To the components of the solar module 3 and in particular the EVA provided therein 13 during a lamination process is in the hot plate 9 and at a corresponding location in the housing 5 an opening 25 intended. In the area of this opening 25 is a monitoring device 27 flanged in the form of a fluorescence measurement and evaluation arrangement for determining information about a cross-linked state of the EVA.

As in 2 shown in detail, includes this monitoring device 27 a lighting device 29 with the help of which a beam 31 from UV light in the spectral range from 320 to 400 nm through the aperture 25 through to the EVA 13 of the solar module 3 is directed. The beam 31 first passes through a first filter 33 which filters out spectral ranges above 400 nm. As a lighting device 29 For example, a low-cost LED can be used. Alternatively, a laser diode may be used, which typically emits in a narrower spectral range, so that possibly on the first filter 33 can be waived.

The one of the lighting device 29 emitted light beam 31 is from a mirror 34 towards the surface of the stack of the solar module 3 directed so that it meets at a different angle at 90 ° to this surface, so that there or at other centers of reflection reflected light 35 not to one beside the lighting device 29 arranged detection device 37 is reflected.

To the ingress of external light from the outside or the crosstalk of light from the lighting device 29 directly to the detection device 37 To prevent it, the entire monitoring device 27 from a housing 39 surrounded and a beam path of the illumination device 29 towards the solar module 3 goes through a mirrored optical partition 41 from a beam path from the solar panel 3 back to the detection device 37 is enough, separated.

If that of the lighting device 29 incoming UV light on fluorescence-active chromophores 43 within the EVA, these are excited and then emit diffuse fluorescent light 45 out. Part of this fluorescent light 45 reaches the detection device 37 , In this case, this detection device 37 a second filter 47 upstream, although the fluorescent light 45 , which mainly has components in the spectral range above 400 nm, transmits, but filters out spectral regions with lower wavelengths below 400 nm. Detection signals of the detection device 37 thus give information about the fluorescence behavior of the EVA. These detection signals can be sent to an evaluation device 38 be derived, which derives therefrom information about the networking state of the EVA and based on this information, the controller 23 the lamination device 2 affected.

3 shows a distribution of a light intensity I as a function of the wavelength λ of an emission spectrum of EVA in different crosslinking states under excitation with UV light in the range of 365 nm. Curves A, B and C thus give the emission spectra at 0% crosslinking, 50% crosslinking and total networking of the EVA again. In addition to a strong peak in the region of the excitation wavelength at 365 nm, it can clearly be seen that an intensity of the emission spectrum in the range of wavelengths of 400 to 500 nm increases markedly with increasing crosslinking of the EVA, which indicates increased fluorescence of the EVA with increasing crosslinking ,

4 roughly schematically illustrates the behavior of the degree of crosslinking V (t) of EVA as a function of the duration t of the lamination process. It can be clearly seen that the degree of crosslinking initially increases from an initially uncrosslinked state as the process progresses, in order then to saturate upon total crosslinking.

While that in 4 As is typical for any lamination process, it was found that the 3 The change in the fluorescence behavior of the EVA shown can only be observed if the lamination process, ie the crosslinking, is carried out largely without the presence of oxygen, for example in a vacuum, as is the case in a laminator, or in a diffusion-tight encapsulation. A cross-linking process on an oxygen-containing atmosphere generally shows no change in the fluorescence behavior.

5 roughly schematically illustrates a section through a device 51 with the help of which information about a degree of crosslinking of EVA, for example, in a finished laminated solar module 3 can be determined. On an optically opaque plate 53 , which does not need to be heated, is the solar module 3 laid and, for example, with a likewise opaque film 55 covered. Through an opening in the opaque plate 53 can light from a first lighting device 29 through a filter 33 through to the solar module 3 be directed. This first light 31 has a wavelength in the emission range of 320 nm to 400 nm and is thus suitable for exciting fluorescence-active centers 43 in the EVA. fluorescent light 45 , which is then isotropic from such centers 43 is emitted, then at least partially, after transmission through a second, for this longer-wave light permeable filter 47 to a detection device 37 ,

In addition to the first lighting device 29 is a second lighting device 57 provided, which light with a wavelength in an emission range of about 400 nm to the solar module 3 shine. While from the first lighting device 29 upcoming short-wave UV light 31 over a mirror 34 as possible deflected so that on the solar module 3 reflected light not to the detection device 37 reaches, is the second lighting device 57 possibly arranged so that the second light emitted by it 59 after reflection on the solar module 3 the detection device 37 achieved, this second light due to its spectral range unhindered by the second filter 47 can be transmitted. The second lighting device 57 can thus together with the detection device 37 be used to reflection and scattering properties of the solar module 3 in the spatial area where the fluorescent light measurement is performed on it. Since the reflection and scattering properties affect how much fluorescent light the detection device 37 achieved, a fluorescence light measurement can thus be calibrated advantageously using the measured reflection and scattering properties. In this way, irrespective of the location where the fluorescent light measurement is carried out, and irrespective of the locally prevailing reflection and scattering properties, information about the excitation by the UV light 31 caused fluorescent light 45 and from this information about the degree of crosslinking of the EVA in the solar module 3 be derived.

Finally, it is pointed out that the terms "comprise", "exhibit" etc. do not exclude the presence of further elements. The term "a" does not exclude the presence of a plurality of objects. The reference signs in the claims are only for better readability and are not intended to limit the scope of the claims in any way.

LIST OF REFERENCE NUMBERS

1

contraption

2

The laminator

3

solar module

5

casing

7

separating edge

9

heating plate

10

heater

11

Front glass

13

EVA film

15

solar cells

17

backsheet

19

pressure membrane

20

pressing device

21

vacuum pump

23

control

25

opening

27

monitoring device

29

(first) lighting device

31

excitation beam

33

first filter

34

mirror

35

reflected light

37

detection device

38

evaluation

39

casing

41

partition wall

43

Fluorescence-active centers / chromophores

45

fluorescent light

47

second filter

51

Networking state measuring device

53

opaque plate

55

opaque foil

57

second illumination device

59

second illumination light

Claims (15)

Process for laminating articles to be encapsulated, in particular solar cells ( 15 ), the method comprising at least the following method steps: a) embedding the articles in crosslinkable polymer material ( 13 ); b) pressing the articles embedded in crosslinkable polymeric material; c) heating the crosslinkable polymer material above 120 ° C; d) Illumination of the Crosslinkable Polymer Material with Light ( 31 ) having a wavelength in an emission range of 320 nm to 400 nm; e) Detecting Fluorescent Light ( 45 ) having a wavelength in an absorption range of 400 nm to 600 nm from the illuminated crosslinkable polymer material; and f) deriving information about a crosslinking state of the crosslinkable polymer material based on the detected fluorescent light, the method steps (d) to (f) being carried out during or after heating the crosslinkable polymer material above 120 ° C. The method of claim 1, wherein the process steps (d) to (f) are repeatedly performed while heating the crosslinkable polymer material above 120 ° C. The method of claim 2, wherein the heating of the crosslinkable polymer material is terminated above 120 ° C after an intensity of detected fluorescent light exceeds a threshold. The method of claim 1, wherein the method steps (d) to (f) are performed within a period of one week after the heating of the crosslinkable polymer material has ended and before the crosslinkable polymer material is exposed to solar radiation or a similarly strong UV source. Method according to one of claims 1 to 4, wherein before or at the beginning of heating the crosslinkable polymer material to above 120 ° C, an initial intensity I ₀ of fluorescent light is measured and wherein during or after the heating, a current intensity I _t of fluorescent light is measured and wherein the information about a crosslinking state of the crosslinkable polymer material is derived from the current intensity and the initial intensity by means of a quotient I _t / I ₀ . Method according to one of claims 1 to 5, wherein the crosslinkable polymer material is illuminated periodically in step (d) and wherein the fluorescent light in step (e) is detected by means of a lock-in method. Method according to one of claims 1 to 6, wherein the crosslinkable polymer material are pressed and heated under oxygen deficiency, in particular under vacuum. Contraption ( 1 ) for lamination of objects to be encapsulated, in particular of Solar cells ( 3 ), the device having at least the following components: a lamination device ( 2 ), the lamination device comprising: - a pressing device ( 20 ) to press the articles during or after being placed in cross-linkable polymeric material ( 13 ), and - a heating device ( 10 ) to heat the crosslinkable polymer material surrounding the embedded articles to a temperature above 120 ° C; A monitoring device ( 27 ), wherein the monitoring device comprises: a lighting device ( 29 ) to illuminate the crosslinkable polymer material surrounding the articles with light having a wavelength in an emission range of 320 nm to 400 nm, - a detection device ( 37 ) to detect fluorescent light having a wavelength in an absorption range of 400 nm to 600 nm from the illuminated crosslinkable polymer material, and - an evaluation device ( 38 ) to determine information about a crosslinking state of the crosslinkable polymer material based on the detected fluorescent light. Apparatus according to claim 8, wherein the apparatus is adapted to perform a method according to any one of claims 1 to 7. Apparatus according to claim 8 or 9, wherein the apparatus is adapted to the lamination device ( 2 ) taking into account the data from the evaluation device ( 38 ) to control information about a crosslinking state of the crosslinkable polymer material. Device according to one of claims 8 to 10, wherein the heating device is a heating plate ( 9 ), wherein the pressing device ( 20 ) acts on one side of the heating plate and wherein the illumination device ( 29 ) and the detection device ( 37 ) are arranged on an opposite side of the heating plate, wherein the heating plate has an opening ( 25 ), through which the illumination device can illuminate the crosslinkable polymer material surrounding the objects received in the pressing device and can pass through the fluorescent light towards the detection device. Contraption ( 51 ) for determining information about a crosslinking state of crosslinkable polymeric material, the device comprising: - a first illumination device ( 29 ) surrounding the articles of crosslinkable polymer material ( 13 ) with first light ( 31 ) with a wavelength in a first emission range from 320 nm to 400 nm, - a second illumination device ( 57 ), surrounding the articles with crosslinkable polymer material with second light ( 59 ) with a wavelength in a second emission range of more than 400 nm, - a detection device ( 37 ) to detect fluorescent light caused by the first light and reflected light having a wavelength in an absorption region of more than 400 nm, respectively, caused by the second light from the illuminated crosslinkable polymer material; and 38 ) to determine information about a crosslinking state of the crosslinkable polymer material based on detected fluorescent light as well as on detected reflected light. Device according to one of claims 8 to 12, wherein the illumination device comprises a light emitting diode and / or wherein the detection device comprises a photodiode. Device according to one of claims 8 to 13, wherein the illumination device is designed and arranged such that emitted by the illumination device light hits at a different angle from 90 ° to a surface of the objects surrounding the crosslinkable polymer material. Device according to one of claims 8 to 14, wherein in a beam path between the illumination device ( 29 ) and the lamination device ( 2 ) a first filter ( 33 ), which filters out light having a wavelength above a cut-off wavelength of 400 nm ± 50 nm, and wherein in a beam path between the lamination device and the detection device ( 37 ) a second filter ( 47 ), which filters out light having a wavelength below the cut-off wavelength.

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