WO2012076064A1

WO2012076064A1 - Device for structuring large format modules

Info

Publication number: WO2012076064A1
Application number: PCT/EP2010/069390
Authority: WO
Inventors: Stefan Schneeberger; Bruno Frei
Original assignee: SOLNEVA SA
Current assignee: SOLNEVA SA
Priority date: 2010-12-10
Filing date: 2010-12-10
Publication date: 2012-06-14
Anticipated expiration: 2013-06-10
Also published as: EP2648872A1; TW201236792A

Abstract

The present invention relates to a device (1) for structuring large format modules, in particular solar modules, comprising means (20, 21) for holding and displacing a large format module (SM) and at least one laser head (31, 32, 33, 34) for structuring the surface of the large format module (SM), the at least one laser head (31, 32, 33, 34) being arranged in a way movable in at least two directions beneath the large format module (SM), in which device at least one laser source (41, 42, 43, 44) is positioned at a fixed position, the laser beams being supplied from the at least one laser source (41, 42, 43, 44) to the at least one laser head (31, 32, 33, 34) by means of a fibre-based guide (51, 52, 53, 54). The present invention also relates to a corresponding method for structuring large format modules.

Description

Device for Structuring Large Format Modules

Technical Field

This invention relates to a device for structuring large format modules, in particular solar modules. More specifically, this invention relates to a device for structuring large format modules, in particular solar modules comprising means for holding and displacing a large format module and at least one laser head for structuring the surface of the large format module, the at least one laser head being arranged in a movable way beneath the large format module.

Background Art

Large format electrical and electronic modules are becoming more and more important, namely in applications in which the surface of the module is one of the major performance criteria. Typical large format modules of this kind are solar modules (sometimes referred to as solar panels) which are nowadays increasingly used for transforming sunlight energy into electricity. Generally speaking, a solar module is a packaged interconnected assembly of so- called solar cells. Basically, solar cells are solid state devices which are capable of using the photovoltaic effect for converting the energy of the sunlight into electricity.

Essentially, most solar cells make use of a semiconductor for absorbing light and converting it into electron-hole pairs. Solar cells can be divided into different groups, based on the type of semiconductor they consist of. Currently, most solar cells use monocrystalline or polycrystalline silicon in a wafer form. However, the high cost of crystalline silicon wafers and the scarce availability of its raw material (the so called polysilicon) have has led to the increasing popularity of solar cells based on thin films of other materials (they are referred to as thin-film solar cells). In such solar cells, these thin films typically have a thickness in the range of micrometers. The most commonly used materials in the manufacturing of thin-film solar cells are amorphous and microcrystalline silicon (a-Si, μ-Si), cadmium telluride (CdTe) and copper indium (gallium) diselenide (better known under the acronyms CIS or CIGS). These semiconductor layers are generally deposited onto either coated glass substrates or flexible substrates such as stainless steel sheets or polymers.

The manufacturing process of thin-film solar modules is generally as follows: The substrate (e.g. a glass plate) is first coated with a first conductive layer. Then, a laser scribing method is used in order to create thin grooves in this layer so that individual cells can be separated from each other. In the next step, a second layer, consisting of a semiconductor material, can be deposited on top of the previous layer. Then, the substrate is again brought into a machine for structuring modules, and the laser scribing method is again used for removing certain parts of the second layer, before a third layer is applied to the module. Finally, a third laser scribing step is needed for finalising the solar module.

Recently, new machines for structuring such thin-film solar modules have been proposed (cf. the European patent application EP 2 139 049). In these new machines, the substrate plate of the solar module is not supported by a supporting means which holds the plate from beneath during the laser scribing steps. Instead, these new machines comprise a new holding means which uses a combination of vacuum and compressed air technology for holding the plate in a fully suspended position. Thanks to this feature, the space beneath the solar module remains completely free and can therefore be used for improving the working efficiency of the laser scribing process.

Figure 1 and Figure 2 show simplified, schematic frontal views of two machines 1 for structuring thin-film solar modules SM following this new proposal. In both these drawings, the reference numeral 1 designates the structuring machine itself. The machine 1 generally comprises a chassis 10 and a holding means 20. This holding means 20 has a number of holding elements 21 which use both air flow and vacuum technology in order to keep the solar module SM in a suspended state and ready to be machined. All details relating to the structure of the machine 1 itself and to the method of suspending the substrate during the machining process can be found in the above-identified document.

In the machine 1 of Figures 1 and 2, laser heads 31 , 32, 33, 34 are disposed beneath the solar module SM. Each of the laser heads 31 , 32, 33, 34 is provided with an optical element 31 ', 32', 33', 34' which allows focusing the laser beam to a desired spot size. In order to be able to structure the surface of the solar module, each of these laser heads 31 , 32, 33, 34 must be able to move in different directions and to provide laser pulses for scribing in the substrate plate of the solar module SM. A serious issue in this context is the speed of the movement of both the solar module SM and the laser heads 31 , 32, 33, 34 since the manufacturing speed is directly proportional to the time needed for moving the solar module SM through the different phases of the process. In other words, the optimisation of the solar panel structuring and manufacturing processes necessarily involves an increase of the movement speed of different components.

According to one of the currently known solutions (which is schematically illustrated in Figure 1 ), four laser sources 41 , 42, 43, 44 are disposed on the frame 10 in such a way that they can provide the laser energy to the laser heads 31 , 32, 33, 34 using a system of multiple mirrors 35, 36, 37, 38. Each of the multiple mirror systems 35, 36, 37, 38 is therefore positioned and oriented in such a way that it can receive and deliver the laser beam from the corresponding laser source 41 , 42, 43, 44 to the solar module SM at any time.

This common solution has important disadvantages, however. Firstly, a mirror system is very sensitive to the vibrations of the frame 10. Strong vibrations can significantly reduce the precision of the laser, and thus very easily result in a poor quality of the scribes. Moreover, such a solution is highly dependent on an (almost) sterile environment because any particles that are found between the laser sources 41 , 42, 43, 44 and the corresponding mirrors 35, 36, 37, 38 can lead to disturbance of the laser beams and also to a diminution of the scribing quality. A second solution from the state of the art (which is schematically illustrated in Figure 2) tries to solve this problem by miniaturising the laser sources 41 , 42, 43, 44 in such a way that they can be fully integrated into the laser heads 31 , 32, 33, 34. Thus, a mirror system as in the previous case is not necessary. The disadvantage of this solution resides mainly in the fact that miniaturised laser sources are quite expensive and still quite difficult to implement. Furthermore, laser heads 31 , 32, 33, 34 with integrated laser sources 41 , 42, 43, 44 are necessarily much heavier than laser heads 31 , 32, 33, 34 which do not bear the laser beam sources. Therefore, they cannot be moved during the scribing process as easily as laser heads 31 , 32, 33, 34 containing only lightweight elements.

If we bear in mind that the manufacturing precision and the manufacturing speed are the main parameters in the production of solar modules, it becomes clear that the above-identified techniques do not provide for a satisfactory solution to this problem.

Disclosure of Invention

It is thus an object of this invention to propose a new and improved device for structuring solar modules that does not present the above-mentioned inconveniences and disadvantages of the prior art.

According to the present invention, these and other objectives are achieved in particular through the features of the independent claims. In addition, further advantageous embodiments follow from the dependent claims and the description.

More particularly, this object is achieved through the invention in that, in a device for structuring large format modules, in particular solar modules, comprising means for holding and displacing a large format module and at least one laser head for structuring the surface of the large format module, the at least one laser head being arranged in a movable way beneath the large format module, at least one laser source is positioned at a fixed position, whereby the laser beams are supplied from the at least one laser source to the at least one laser head by means of a fibre-based guide.

The advantage of this invention, among other things, resides in the fact that the laser heads which are used for scribing can be kept very small and lightweight so that their weight does not have any negative impact on their mobility and the scribing precision. At the same time, the disadvantages of a mirror system can also be completely avoided so that the device for structuring solar modules according to this invention can be robust and can provide for a very precise scribing.

In an embodiment variant, the laser guide is a glass fibre, especially an optical fibre. This embodiment variant has the advantage, inter alia, that no dust particles or other physical interference can come across the beam path and therefore jeopardise the laser beam quality. Moreover, the short distance between the laser output and the solar module makes such an arrangement very robust against vibrations. Furthermore, the lightweight quality of the laser heads makes possible their fast and precise movement over a large format. Therefore, this solution with a completely fixed large format module and fast moving laser heads is very robust thanks to the stable working position. Finally, this solution also allows for a very short setup and adjustment time which results in a very low cost of ownership.

In particular, the glass fibre can be a single-mode optical fibre. A single-mode optical fibre has the advantage, among other things, that it produces a good beam quality for small spot sizes and that it therefore enables a precise scribing resulting in a small dead zone. Small dead zones on the module in turn result in a higher efficiency of the module with respect to common solutions. Moreover, another advantage of the single-mode optical fibre is a long depth of focus and therefore large tolerances for the positioning of the module.

The optical fibre can preferably be a large mode area (LMA) fibre (e.g. step index LMA fibre, photonic crystal fibre, air clad fibre, multicore fibre, or chirally-coupled core fibre (CCC-fibre)). The use of an LMA fibre has the advantage, among other things, that it allows for a high coupling efficiency between the laser source and the fibre and therefore for a reduced need of laser power. In addition, LMA fibres have larger tolerances for light coupling optics, an efficient transport of short pulses (in the nanosecond and picosecond range) with relatively high energy. Therefore, this solution enables high peak powers.

In another embodiment variant, the laser beams supplied by the laser sources are in the infrared and/or ultraviolet and/or green light spectra.

The advantage of using the infrared laser sources is, among other things, that they are very beneficial for scribing the first scribing line (P1 ) of the module through the glass substrate. Thanks to the use of these infrared laser sources, a very clean first scribing line (P1 ) can be achieved, so that no suction for particle removal is required during the manufacturing process. Furthermore, laser sources in the infrared range are available on a high industrial level which makes them not only very robust and reliable, but also relatively inexpensive.

On the other hand, the advantage of using the ultraviolet laser sources is, among other things, that they can also be used for scribing the first scribing line (P1 ) through the glass substrate. The ultraviolet laser sources have also a very efficient material ablation (with a factor 5 to 10) which makes them even better than infrared laser sources for scribing this first scribing line (P1 ). Therefore, ultraviolet laser sources can be operated at a low average laser power.

Finally, the laser beams supplied by the laser sources can also be in the visible light spectrum, especially in the green spectrum. Using a laser source in the visible spectrum has the advantage, among other things, that it enables an easy and safe scribing of the second (P2) and third (P3) scribing line both through the glass substrate and the first thin film layer. Thanks to the use of a visible light laser source, the structuring of the solar module can easily be performed from beneath the module, through the glass substrate and without any damage on the first layer. In a further embodiment variant, the laser sources provide pulsed laser beams. The advantage of this embodiment variant is, inter alia, that an efficient material ablation can be achieved thanks to a high peak power of pulsed laser beams. Therefore, the machining can be performed with a moderate average laser power which greatly reduces heat effects on layer material and further increases the machining quality.

Preferably, the pulse duration of the laser beams is in the nanosecond or picosecond range.

The advantage of using pulsed laser beams with the duration in the nanosecond range is, among other things, that the high peak power of such a laser beam enables an efficient material ablation thanks to its high peak power. Therefore, a moderate average laser power and greatly reduced heat effects on material can be achieved.

Also, using the pulse duration of the laser beams in the picosecond range has the advantage, among other things, that the heat affected zone on the material for processing from the film side can be further minimised such that the machining quality can be further improved.

In another embodiment variant, the device comprises a modulation means for modulating the pulse frequency of the laser beams as a function of the movement speed of the laser head. At constant pulse energy and pulse duration, this embodiment variant has the advantage, inter alia, that an optimised processing speed, compared with constant velocity, can be achieved. This allows for a flexible processing speed in the machining process.

The device according to the invention is particularly adapted for structuring thin-film (TF) solar modules.

At this point, it should be stated that, besides the device for structuring solar modules according to the above-identified embodiments of the invention, the present invention further relates to a method of structuring solar modules using the device according to the present invention. In particular, the invention also relates to a method for structuring large format modules, in particular solar modules, in which a large format module is held and displaced by a holding means and in which the surface of the large format module is structured by at least one laser head, the at least one laser head being arranged in a way movable in at least two directions beneath the large format module, and the laser beams being supplied from the at least one laser source to the at least one laser head from at least one fixed laser source by means of a fibre-based guide.

Brief Description of Drawings

The present invention will be explained in more detail, by way of example, with reference to the drawings in which:

Figure 1 is a schematic frontal view of a device for structuring solar modules from the state of the art;

Figure 2 is a schematic frontal view of another device for structuring solar modules from the state of the art; and

Figure 3 is a schematic frontal view of a device for structuring large format modules according to an embodiment of the present invention.

Description of Specific Embodiments of the Invention

Figure 3 illustrates a device for structuring large format modules according to an embodiment of the present invention.

In Figure 3, the structuring device itself bears the reference numeral 1 . Similar to the devices illustrated in Figures 1 and 2, the device 1 according to the invention comprises a chassis 10 and a holding means 20. The holding means 20 comprises a number of holding elements 21 which use a combination of vacuum and compressed air in order to keep the large format module (e.g. a thin film solar module) SM in a suspended state and ready to be machined. The device 1 can obviously comprise other elements (some of which are illustrated in Figure 3, e.g. adjustable feet for a precise positioning of the device). As these additional elements of the device 1 are not decisive for the invention, their description will be omitted for the sake of simplicity. Details about the structure and the function of such devices should be well known to a skilled person.

The device 1 of Figure 3 comprises four laser heads 31 , 32, 33, 34 which are disposed beneath the large format module SM. It is obvious to a skilled person that the number of laser heads 31 , 32, 33, 34 can be bigger or smaller than four. However, four laser heads 31 , 32, 33, 34 are a good compromise between the need to have different lines scribed at the same time and the need to keep space for quick movements of laser heads 31 , 32, 33, 34, as well as the cost of laser sources.

Laser heads 31 , 32, 33, 34 have movement means (not illustrated) which allow them to move beneath the large format module SM such that they can structure the surface of the module SM. In particular, laser heads 31 , 32, 33, 34 can be mounted on a beam or girder 39 which can move in one direction. Each of the laser heads 31 , 32, 33, 34 can further move on the beam in a direction which is perpendicular to the movement direction of the beam. However, any other appropriate movement system can be used in the device 1 according to the invention. In particular, a system is also possible in which each laser head 31 , 32, 33, 34 is connected to an arm that is fully pivotable in all three spatial directions.

Each of the laser heads 31 , 32, 33, 34 comprises optical elements 31 ', 32', 33', 34' which allow for focusing the laser beams coming out of the laser heads 31 , 32, 33, 34. The optical elements 31 ', 32', 33', 34' can obviously be replaced by any appropriate focusing means. In particular, the optical elements 31 ', 32', 33', 34' can be remotely controlled dynamically, in such a way that the focus of the laser beams can be dynamically adapted to different production phases. The device 1 further comprises four laser sources 41 , 42, 43, 44 which are fixedly disposed at the frame 10 - one corresponding to each laser head 31 , 32, 33, 34. Of course, the number of laser sources 41 , 42, 43, 44 can be bigger or smaller than four and not necessarily correspond to the number of laser heads 31 , 32, 33, 34. Preferably, one single laser source will deliver laser beams for all laser heads 31 , 32, 33, 34. However, the number of laser sources 41 , 42, 43, 44 will usually correspond exactly to the number of laser heads 31 , 32, 33, 34. The laser sources 41 , 42, 43, 44 can in particular provide laser beams in any one of the ultraviolet and/or green and/or red light spectra. It is also imaginable, however, to have laser sources 41 , 42, 43, 44 that can provide laser beams in different spectra.

Also, the laser sources 41 , 42, 43, 44 can be adapted to provide pulsed laser beams, especially in the nanosecond or in the picosecond range. However, it is also possible to use laser sources 41 , 42, 43, 44 whose output are non-pulsed laser beams. Advantageously, if the pulsed laser beams are used, the device 1 can comprise a modulation means (not illustrated) for modulating the pulse frequency of the laser beams as a function of the movement speed of the corresponding laser head 31 , 32, 33, 34.

The laser sources 41 , 42, 43, 44 of the device 1 are coupled to the laser heads 31 , 32, 33, 34 by means of a fibre-based guide 51 , 52, 53, 54. Preferably, one single laser source can be coupled to four laser heads 31 , 32, 33, 34 by means of four fibre-based guides 51 , 52, 53, 54. However, usually, and as illustrated in Figure 3, one laser source 41 , 42, 43, 44 is directly coupled to one corresponding laser head 31 , 32, 33, 34. However, it is also conceivable to adapt the device 1 in such a way that one laser source 41 , 42, 43, 44 is coupled to more than one laser head 31 , 32, 33, 34 or that a multitude of laser sources 41 , 42, 43, 44 is coupled to a single laser head 31 , 32, 33, 34. Also, the coupling of the laser sources 41 , 42, 43, 44 to the laser heads 31 , 32, 33, 34 does not need to be direct because different auxiliary elements (such as amplifiers, etc.) can be used between the laser sources 41 , 42, 43, 44 and the laser heads 31 , 32, 33, 34. The fibre-based guides 51 , 52, 53, 54 are preferably glass fibres, e.g. optical fibres. Any standard optical fibres can be used. However, a single- mode optical fibre, especially a large mode area (LMA) fibre has got particular advantages for the present invention. It is conceivable that all fibre-based laser guides 51 , 52, 53, 54 of the device 1 are of the same type. However, different guide types can obviously be used for any one of the fibre-based guides 51 , 52, 53, 54.

Thanks to the device 1 for structuring large format modules according to the present invention, the machining process can be extremely optimised and the production quality of modules increased. Furthermore, the robustness of the device 1 makes it also usable in difficult environments. Thanks to the fibre-guided laser beams, the whole installation and adjustment process can be kept easy and quick which, again, increases the productivity of the device 1 . In addition, the scribing preciseness leads to smaller dead zones which directly results in an increase in the efficiency of the modules.

Although the present disclosure has been described with reference to particular means, materials and embodiments, one skilled in the art can easily ascertain from the foregoing description the essential characteristics of the present disclosure, while various changes and modifications may be made to adapt the various uses and characteristics as set forth in the following claims.

Claims

1 . Device (1 ) for structuring large format modules, in particular solar modules, comprising means (20, 21 ) for holding and displacing a large format module (SM) and at least one laser head (31 , 32, 33, 34) for structuring the surface of the large format module (SM), the at least one laser head (31 , 32, 33, 34) being arranged in a way movable beneath the large format module (SM), characterised in that at least one laser source (41 , 42, 43, 44) is positioned at a fixed position, whereby the laser beams are supplied from the at least one laser source (41 , 42, 43, 44) to the at least one laser head (31 , 32, 33, 34) by means of a fibre-based guide (51 , 52, 53, 54).

2. Device according to claim 1 , characterised in that the laser guide (51 , 52, 53, 54) is a glass fibre, especially an optical fibre.

3. Device according to claim 2, characterised in that the glass fibre is a single-mode optical fibre.

4. Device according to claim 2 or 3, characterised in that the optical fibre is a large mode area (LMA) fibre.

5. Device according to any one of the claims 1 to 4, characterised in that the laser beams supplied by the laser sources (41 , 42, 43, 44) are in the ultraviolet and/or green and/or red light spectra.

6. Device according to any one of the claims 1 to 5, characterised in that the laser sources (41 , 42, 43, 44) provide pulsed laser beams.

7. Device according to claim 6, characterised in that the pulse duration of the laser beams is in the nanosecond or picosecond range.

8. Device according to claim 6 or 7, characterised in that it comprises a modulation means for modulating the pulse frequency of the laser beams as a function of the movement speed of the laser head (31 , 32, 33, 34).

9. Device according to any one of the claims 1 to 8, characterised in that the large format module (SM) is a thin-film (TF) solar module.

10. Method for structuring large format modules, in particular solar modules, in which a large format module (SM) is held and displaced by a holding means (20, 21 ) and in which the surface of the large format module (SM) is structured by at least one laser head (31 , 32, 33, 34), the at least one laser head (31 , 32, 33, 34) being arranged in a way movable in at least two directions beneath the large format module (SM), characterised in that the laser beams are supplied from the at least one laser source (41 , 42, 43, 44) to the at least one laser head (31 , 32, 33, 34) from at least one fixed laser source (41 , 42, 43, 44) by means of a fibre-based guide (51 , 52, 53, 54).