Patent Publication Number: US-2012027925-A1

Title: Method and device for producing serially connected solar cells

Description:
The invention relates to a method for production of series-connected thin-film solar cells, which method has the steps of arrangement of a semi-finished product having a rigid mount substrate on a receptacle, introduction of the semi-finished product into a deposition chamber having a deposition device, and deposition of a material layer onto the semi-finished product. 
     Solar cells based on thin-film technology are distinguished in particular by the use of little material to produce the active layers and by a high potentially achievable efficiency. In order to reduce resistive losses and to produce a high output voltage, the active layers of the solar cells are normally structured on the substrate and are connected in series with one another. 
     Rigid materials can be used as a substrate for producing solar cells based on thin-film technology since this allows the very thin layers to be arranged on a firm base, thus making it possible to increase the mechanical robustness and to simplify handling during manufacture. 
     One method for producing a circuit of thin-film solar cells with glass substrates is known from WO 2007/044555 A2. In this case, active and conductive layers are deposited onto a substrate in a first process step, wherein individual layers, or all the layers, are then separated by a laser or mechanical scoring in order to apply an additional conductive layer, by a printing process or by electroplating, in order to deliberately connect specific active layers. 
     In an alternative method, the deposition process is in each case followed by a cutting process. In this case, the layer most recently deposited in each case, possibly together with further layers, is separated in order to make it possible to deliberately introduce conductive or active material into the separation area with the subsequent layer. Once the uppermost conductive layer, the front contact, has been applied, this layer, possibly together with further layers, is then cut open in order to prevent a short circuit of the front contacts of adjacent solar cells. 
     In principle, this makes it possible to manufacture solar cells using thin-film technology on glass substrates. However, it has been found that methods such as these are particularly complex and are therefore highly costly, since the respectively applied layers must be partially removed again in an additional process, for connection purposes. Separate, expensive laser cutting installations or mechanical scoring installations are required for this purpose. Furthermore, the glass substrate must, according to the method, be transferred in each case between a deposition process and a cutting process, since the deposition process is carried out in a vacuum chamber, and the cutting process is carried out in separate apparatuses. The transfer is particularly complex since it is necessary in each case to pass through a vacuum lock and, furthermore, the substrate temperature must be matched to the respective process temperatures used during deposition in a vacuum and during the cutting process. 
     Furthermore, passing the substrate repeatedly into and out of the vacuum lock can increase the risk of contamination both of the substrate and of the deposition device and of the cutting apparatus. This can lead to poorer process quality and to waste production. 
     WO 2007/085343 A1 discloses a method for production of series-connected solar cells having flexible substrates, in which the substrate is applied to a curved contact surface in a deposition device, and is shadowed with respect to the deposition device by means of at least one stressed wire which is placed on the substrate. The material layer to be applied is therefore structured during the deposition process itself. The stressed wire can advantageously be prestressed with respect to the flexible substrate such that this results in a sufficiently broad contact surface, in whose area no material can be deposited, by the deformation of the substrate, instead of simple line contact. 
     Furthermore, both the flexible substrate and the wire of the deposition device can be fed continuously or quasi-continuously, in order to allow continuous production of a structured material layer on the flexible mount substrate, in a continuous process. 
     However, it has been found that such solar cells with flexible substrates can be produced on an industrial scale only at high cost. In addition, solar cells such as these have only limited mechanical natural robustness and, for some applications, must therefore be provided with separate mount and protective layers. 
     The method is also not particularly suitable for production of thin-film solar cells with rigid substrates, since, because of the lack of capability for curvature and the lack of elasticity on the substrate surface, the wire cannot adequately shadow the rigid substrate, with respect to the deposition device, which can result in faults, in particular short circuits, in the structure of the material layer to be deposited. 
     In contrast, the production of solar cells on glass substrates is widespread, and has been proven on a large technological scale. However, it is complex and expensive to connect such solar cells in series. 
     Against this background, the invention is based on the object of specifying an improved method for production of thin-film solar cells with rigid substrates, which is as suitable as possible for advantageous, automated manufacture. A further aim is to specify an apparatus which is suitable for carrying out this method. 
     According to the invention, this object is achieved by a method for production of series-connected thin-film solar cells having the following steps:
         arrangement of a semi-finished product having a rigid mount substrate on a receptacle;   introduction of the semi-finished product into a deposition chamber having a deposition device;   application of a masking device having at least one masking means, which is in the form of a strand and is prestressed in the longitudinal direction, to a surface of the semi-finished product facing the deposition device;   partial shadowing of the surface of the semi-finished product by means of the masking device from the deposition device in order to structure a material layer to be deposited;   deposition of the material layer onto the semi-finished product; and   release of the masking device from the surface of the semi-finished product.       

     In this way, the object of the invention is achieved completely. 
     Specifically, according to the invention, the masking device with the masking means in the form of a strand results in particularly good and reliable shadowing of the semi-finished product with the rigid mount substrate with respect to the deposition device. In this case, the masking means in the form of a strand must have a minimum thickness of 20 micrometres. In addition, adequate elasticity must be provided in order to create a flat contact (instead of a linear contact) between the rigid mount substrate and the masking means in the form of a strand. Otherwise, it is no longer possible to ensure adequate shadowing, thus resulting in a risk of short circuits. 
     According to the invention, the material layer to be deposited can be structured during the deposition process itself. This avoids the need for separate cutting processes for structuring a material layer, even in the case of thin-film solar cells with rigid substrates. Advantageous manufacture, which can be automated, can be achieved by the capability to use installations which have been proven on a large technological scale, for production of solar cells on glass substrates. 
     The masking means in the form of a strand ensures a high level of process reliability since reliable shadowing is ensured even when the substrate is only slightly curved, thus resulting in clean, uncoated separating surfaces, preventing short circuits, during the coating process. 
     For the purposes of this application, a “rigid mount substrate” means a mount substrate which, in contrast to a flexible mount substrate, can be bent only to a limited extent, that is to say allowing maximum bending with a bending radius of &gt;100 cm. By way of example, this could be a plate composed of a glass, a glass ceramic material or a wafer. In the narrower sense, this means a mount substrate which allows maximum bending with a bending radius of &gt;20 cm. Greater bending than this leads to destruction or damage, for example to continuous deformation, of the substrate. It has been found that glass plates tend to fracture with a smaller bending radius, and mount substrates in the form of rigid plastic panels or metal plates are damaged, for example by fracturing or being permanently deformed. 
     As already mentioned, the rigid mount substrate may be a substrate which consists of a glass material, a glass ceramic material, a wafer, a plastic or a metal. 
     This makes it possible to use a wide range of glass materials, glass ceramic materials or else wafers in order to form the rigid mount substrate. It is preferably possible to use materials which are particularly suitable for electronic applications, such as borosilicate glass with a proportion of barium oxide and aluminium oxide. Suitable glass materials and glass ceramic materials form a highly effective diffusion barrier, which means that there is no need for additional measures for this purpose. In addition, wafers can be used as mount substrates. 
     Furthermore, in principle, plastic panels and metal plates are also suitable as mount substrates. 
     In one preferred development, the masking means which is in the form of a strand has a plurality of filaments which rest on one another. For the purposes of this application, a “filament” means any type of elongated element. This may therefore be a metal wire, a plastic thread, for example consisting of polyamide, or a high-strength material such as aramid. It is also possible to use other inorganic materials which can conceivably be drawn out to form threads or fibres, such as C, BN, SiC etc. In any case, a cohesive, tension-resistant filament must be created, which has a thickness of at least 20 μm. In addition, particularly when using only a single filament, this must be deformable when placed on the rigid mount substrate to such an extent as to create an area contact, not only a linear contact, between the rigid substrate and the masking means in the form of a strand. Otherwise, adequate shadowing is not ensured, thus creating a risk of short circuits. 
     When a plurality of filaments resting on one another are used, this itself results in intermediate spaces which are screened from the outside and therefore ensure good screening from the plasma. 
     In one advantageous development of the invention, the semi-finished product has convex curvature with respect to the deposition device. 
     This makes it possible to ensure that a force component is created in the direction of the surface of the semi-finished product when the masking means is applied, which is prestressed in the longitudinal direction. This makes it possible to prestress the masking means particularly effectively with respect to the semi-finished product, thus resulting in even better shadowing of the surface of the semi-finished product with respect to the deposition device. 
     In this context, it should be noted that the bending stresses in the semi-finished product with the rigid mount substrate can remain considerably below the critical strength levels. Taking account of the high stiffness of the rigid mount substrate, little curvature can in consequence be achieved, although this can contribute considerably to further improving the process reliability. 
     In one preferred development of the invention, the at least one masking means carries out a relative movement in the longitudinal direction of the masking means with respect to the semi-finished product during the deposition of the material layer. 
     This measure allows particularly effective shadowing of the semi-finished product with respect to the deposition device to be achieved, and the process-dependent deposition of the material layer to be deposited on the masking means can be considerably reduced. This allows the process quality to be further improved and the effort for cleaning the masking device with the masking means can be reduced. 
     For the purposes of this application, the relative movement between the semi-finished product and the masking means in the longitudinal direction of the masking means can take place both by movement of the semi-finished product with respect to the stationary masking means or by movement of the masking means with respect to the stationary semi-finished product, as well as by simultaneous movement of the semi-finished product and of the masking means. In this case, the movements may be in the opposite sense, or else in the same sense, with different absolute velocities. 
     According to a further refinement of the invention, the at least one masking means is moved in and out continuously or quasi-continuously in the longitudinal direction. 
     This allows the method to be automated particularly well, since the masking means can be fed in and out for example using a revolving process or a roll-to-roll process. 
     In one preferred development of the invention, the at least one masking means is guided by at least one guide roller or is aligned by at least one centring means. 
     This allows the masking means to be fed in particularly accurately and deliberately, allowing shadowing losses to be minimized, and thus making it possible to improve even further the process accuracy and quality. The process of the filaments of the masking means resting on one another can likewise be assisted by suitable guidance and alignment of the masking means by guide rollers and/or centring means, in order to further improve the effectiveness of the shadowing. 
     According to a further refinement of the invention, the at least one masking means is loaded by a hold-down device transversely with respect to its longitudinal direction, essentially at right angles to the surface of the semi-finished product. 
     This measure also makes it possible to produce a force component at right angles to the surface of the semi-finished product, assisting the process of the masking means resting firmly on the surface of the semi-finished product, and therefore making it possible to further improve the shadowing of the surface of the semi-finished product with respect to the deposition device. 
     In an alternative refinement of the invention, the hold-down device has the at least one guide roller or the at least one centring means. 
     This allows various functions, such as holding down, alignment and guidance, to be combined, thus making it possible to considerably simplify the manufacturing process. 
     In one advantageous development of the invention, the at least one masking means is prestressed in the longitudinal direction by a stressing means, in particular a spring. 
     This allows the prestress to be applied particularly easily, for example by the stressing means acting directly on the masking means with its filaments, or by the stressing means interacting with the guide roller or the hold-down device, in order to indirectly introduce a prestress into the masking means. 
     According to a further refinement of the invention, a plurality of material layers are deposited onto the semi-finished product using a plurality of deposition chambers. 
     This makes it possible to use deposition chambers which are matched to the deposition process of the respective layer to be deposited, thus making it possible to reduce the cleaning or rinsing effort, resulting in improved manufacturing productivity. In particular, it is possible to use highly automated cluster or linear arrangements with a plurality of specialized deposition chambers for manufacture. 
     In one expedient development of the invention, the at least one masking means is offset transversely with respect to its longitudinal direction on the surface of the semi-finished product between the deposition of the material layers, in order to allow contact or separation of specific material layers. 
     This allows series-connected thin-film solar cells to be manufactured particularly effectively since each material layer can now be structured separately, and the previous separating structure for deposition of a new material layer can be released. This allows material to be deposited to adhere to the old separating structure, thus making it possible to make contact with different material layers particularly effectively and easily. 
     In one advantageous development of the invention, the deposition of the material layers and the offsetting of the at least one masking means are carried out in a process gas atmosphere or in a vacuum. 
     There is therefore no need to remove the semi-finished product and the masking device from the process gas atmosphere or the vacuum in order to offset the masking means. This makes it possible to reduce the manufacturing time, and production can be automated even better. Furthermore, lock processes for matching the semi-finished product or the masking device to the process conditions can be avoided, contamination is reduced, and fewer process residues can escape into the environment. In addition, the substrate remains at the same temperature, which is advantageous for component quality. 
     According to a further refinement of the invention, the offsetting of the at least one masking means is carried out in a separate offset chamber. 
     This makes it possible to use a specialized offset chamber in order to improve the manufacturing productivity even further. Furthermore, this improves the series-production compatibility of the method, since known deposition chambers can now be used, without any special fittings for offsetting the masking means. 
     In one expedient development of the invention, a transfer takes place between the deposition and the offsetting, during which the semi-finished product is still subject to the process gas atmosphere or the vacuum. 
     This measure allows the manufacturing steps to be carried out even for series-production-compatible specialization with a plurality of deposition chambers, an offset chamber and a transfer between the deposition and the offsetting, while still in the process gas atmosphere or in the vacuum. 
     According to a further refinement of the invention, dirt or residues of the deposited material layers are removed from the masking device by cleaning processes, in particular etching processes. 
     This allows the cleaning of the masking device to be integrated in the manufacturing process, and, in particular, established technologies and existing cleaning facilities for the individual chambers can be used for this purpose. 
     The object of the invention is also achieved by an apparatus for production of series-connected thin-film solar cells having at least one deposition chamber having a deposition device, having a receptacle for holding a semi-finished product with a rigid mount substrate, in particular a mount substrate consisting of a glass material, and having a masking device which can be fitted to the semi-finished product, wherein the masking device has at least one masking means which is in the form of a strand, can be prestressed in the longitudinal direction and can be aligned with respect to the semi-finished product for partial deposition of the semi-finished product with respect to the deposition device. 
     According to one development of the apparatus according to the invention, the masking means which is in the form of a strand has a plurality of filaments which rest on one another. 
     This improves the shadowing even further. 
     According to a further embodiment of the apparatus according to the invention, the receptacle for holding the semi-finished product has convex curvature with respect to the deposition device. 
     In one expedient development of the apparatus according to the invention, this apparatus has a plurality of masking means at a distance from one another. 
     In one advantageous development of the apparatus according to the invention, this apparatus has a plurality of deposition chambers for deposition of the material layers, an offset chamber with an offset device with offset means for offsetting the at least one masking means transversely with respect to its longitudinal direction relative to the surface of the semi-finished product, and a handling chamber with a handling device for feeding the semi-finished product into the chambers. 
     According to a further refinement of the apparatus according to the invention, a vacuum can be applied or a process gas can be supplied to the chambers. 
     An apparatus such as this allows the method according to the invention to be carried out in such a way as to allow thin-film solar cells to be produced on rigid substrates in an improved advantageous manner, which can be automated. 
     It is self-evident that the features of the invention mentioned above and those which are still to be explained in the following text can be used not only in the respectively stated combination but also in other combinations or on their own, without departing from the scope of the present invention. 
    
    
     
       Further features and advantages of the invention will become evident from the following description of preferred exemplary embodiments, and with reference to the drawings, in which: 
         FIG. 1  shows a sequence of layer structures of a semi-finished product during the production of solar cells using the method according to the invention; 
         FIG. 2  shows a schematic layer structure of integrated-connected thin-film solar cells, indicating the masking means positions; 
         FIG. 3  shows a section through various masking means for carrying out the method according to the invention; 
         FIG. 4  shows an arrangement for guiding and aligning the masking means; 
         FIG. 5  shows a further arrangement for guiding and aligning the masking means; 
         FIG. 6  shows a schematic section through a deposition chamber according to the present invention, along the line VI-VI in  FIG. 7 ; 
         FIG. 7  shows a schematic section through a masking device along the line VII-VII in  FIG. 6 ; 
         FIG. 8  shows a schematic section through an offset chamber according to the present invention along the line VIII-VIII in  FIG. 9 ; 
         FIG. 9  shows a schematic section through an offset device along the line IX-IX in  FIG. 8 ; 
         FIG. 10  shows two schematic illustrations of an offset chamber according to the invention; 
         FIG. 11  shows a further schematic illustration of a deposition chamber according to the invention; 
         FIG. 12  shows a schematic flowchart of a method according to the invention; 
         FIG. 13  shows a schematic illustration of an apparatus for carrying out the method according to the invention; and 
         FIG. 14  shows a further schematic flowchart of the method according to the invention. 
     
    
    
       FIG. 1  shows a sequence of layer structures of a semi-finished product, which is annotated with the number  10 , during the production of series-connected thin-film solar cells, using the method according to the invention. 
     In  FIG. 1   a , the semi-finished product  10  consists only of a rigid mount substrate. Masking means  30   a ,  30   b  with filaments  32 ,  34  are applied, and are used for structuring a material layer to be deposited. 
       FIG. 1   b  shows the state of the semi-finished product  10 ′ for example after a first deposition process. In this case, a rear contact layer  14   a ,  14   b  has been applied, which is structured corresponding to the masking means  30   a ,  30   b  in  FIG. 1   a . An offset process has resulted in the masking means  30   a ′,  30   b ′ assuming a new position on the surface of the semi-finished product, directly alongside their old positions, in order to structure a next layer to be deposited. 
       FIG. 1   c  illustrates the semi-finished product  10 ″ after a second deposition process. In this case, an active layer  16   a ,  16   b  has been deposited in a structured form. Another offset process has resulted in the masking means  30   a ″,  30   b ″ assuming a new position, and a third material layer to be deposited can now be structured by them. 
       FIG. 1   d  shows the layer structure of the semi-finished product  10 ′″ after this deposition process. A front contact layer  18   a ,  18   b  has been deposited in a structured form. This results in an example of a structure of thin-film solar cells with a mount substrate  12 , a structured rear contact layer  14 , a structured active layer  16  and a structured front contact layer  18 . The partial shadowing and therefore the structuring of the material layers  14 ,  16 ,  18  has now resulted in the production of a series contact between two solar cell arrangements  14   a ,  16   a ,  18   a  and  14   b ,  16   b ,  18   b , since the front contact  18   a  of one solar cell arrangement is connected to the rear contact  14   b  of the second solar cell arrangement. 
     The arrangement as shown in  FIG. 1  should be understood only as being explanatory and not in a restrictive sense since, in particular, the active layer  16  can be formed from a plurality of sublayers. The rear contact layer  14  advantageously consists of conductive, reflective materials such as silver or aluminium, while the front contact  18  is preferably formed from conductive, transparent materials, such as aluminium-doped zinc oxide. 
     In the case of thin-film solar cells, the individual layers are formed by deposition methods and other suitable coating and conversion methods. Chemical gas phase deposition is particularly suitable, for example plasma-assisted chemical gas phase deposition or physical gas phase deposition, for example vapour deposition or sputtering. 
     In this case, a thin film means thin layers of solid substances in the micrometre to nanometre range, at least those which are considerably thinner than a mount substrate. It should also be added that these thickness ratios are not shown to scale in the figures, in order to assist understanding. 
       FIG. 2  shows a schematic series-connected solar cell arrangement having a further layer sequence of a semi-finished product  10  during the production of thin-film solar cells. The active layer  16  is in this case further subdivided in the form of p-i-n junctions. A junction such as this may, for example, have an n-layer  20   a ,  20   b ,  20   c  with n-doped silicon, an intrinsic absorber layer  22   a ,  22   b ,  22   c  adjacent to it with undoped silicon and, finally, a p-layer  24   a ,  24   b ,  24   c  with p-doped silicon. 
     Amorphous or crystalline silicon, in particular also microcrystalline or nanocrystalline silicon, can be used for solar cells based on silicon. 
     The illustrated layer structure should be understood only as an exemplary embodiment; the active layer of thin-film solar cells based on semi-finished products with rigid substrates can likewise contain thin layers with alternative materials such as gallium arsenide, cadmium telluride or, based on CIGS technology, copper, indium, gallium, sulphur or selenium. It is likewise feasible to provide p-n junctions instead of the p-i-n junctions. 
     It is also self-evident that the method according to the invention can also be used to produce so-called tandem cells or packed solar cells with a plurality of p-i-n or p-n junctions formed one on top of the other, in order to make it possible to produce solar cells with a higher energy yield. 
     Furthermore, it is self-evident that the mount substrate  12  can also be used as a mount for other passive and active components, such as protection diodes or contact connections, or else can be used to hold elements for protection against environmental influences, for example front covers or encapsulation arrangements. 
     It is also feasible to use the method according to the invention to suitably connect material layers on the semi-finished product in parallel, thus allowing higher current levels instead of a higher output voltage, as is intended to be achieved by series connection. Any desired combinations of parallel connection and series connection are also feasible. 
     Indicated by dashed circles,  FIG. 2  also shows the various positions to be assumed by the masking means  30   a ,  30   b  during production according to the invention of the solar cells  11   a ,  11   b ,  11   c . As described above, structuring can be achieved by shadowing during a deposition process and subsequently offsetting the masking means  30   a ,  30   b , such that the p-layer  24   a  of the solar cell  11   a  makes contact with the n-layer  20   b  of the solar cell  11   b , and thus allows the solar cell  11   a  to be connected in series with the solar cell  11   b.    
     It should be noted that once again for clarity reasons, the masking means  30  have not been illustrated to scale since, in general, the masking means  30  is considerably thicker than the layer thickness of the material layers to be deposited. 
     In this context, the normal dimensions of the solar cell  11   b  produced according to the invention will be described, without any restriction to generality. The cell width is annotated  26  in  FIG. 2  and can typically, for example, be in the range from 8 to 12 mm, in particular about 10 mm. In contrast, the process width is annotated  28 , as a measure of the losses per unit area of the solar cell, and also of the efficiency loss that is governed by the process. In consequence, in the case of the solar cell  11  which is illustrated by way of example and is produced using a method according to the invention, the process width  28  results from the double offset of the masking means  30 , that is to say from about three times the width of the masking means  30 . 
     In  FIGS. 1 and 2 , the masking means  30  each have two filaments  32 ,  34  which, for example, may each have a diameter of 0.03 mm to 0.2 mm. In this example, this results in a process width  28  of about 0.18 mm to 1.2 mm, which can be subtracted from the cell width  26 , for efficiency analyses. In consequence, depending on the number and size of the filaments of the masking means  30 , the method according to the invention makes it possible to achieve a low loss per unit area of from about 12% to values considerably less than 5%. 
       FIG. 3  shows possible refinements of the cross section of the masking means  30   a ,  30   b  in the form of a strand. The masking means  30   a  and  30   b  each have 3 filaments which, according to the invention, rest on one another. 
     The masking means  30   a  has three filaments  32   a ,  34   a ,  36   a  which are arranged on one plane. This arrangement on the surface  74  of the semi-finished product  10  is particularly highly suitable for preventing short circuits in the material to be deposited. In the ideal, there are three line contacts, and a sufficiently large uncoated area can be formed between them. Even if one of the three line contacts fails, for example by a filament lifting off the surface, thus resulting in the material layer to be deposited entering the area to be shadowed, the other filaments can still allow the surface  74  to be structured. 
     According to  FIG. 3 , the masking means  30   b  has a filament  34   b  which does not itself rest on the surface  74  of the semi-finished product  10 , but is particularly suitable for pressing the filaments  32   b ,  36   b  securely onto the surface  74 . In this case, because the filament  34   b  rests on the filaments  32   b  and  36   b  of the area to be shadowed, this can also be maintained if the filament  32   b  and the filament  36   b  were not to rest on one another. 
     The filaments  32 ,  34 ,  36  illustrated in  FIG. 3  all have a circular cross section. This should not be considered a restriction, and, in fact, it is possible to also use filaments with a different shape to this, for example those with oval cross sections, rectangular, square or triangular cross sections, with or without rounded edges. In particular, this makes it possible to increase the number of possible line contacts. 
     It is also possible to provide filaments with different cross-sectional shapes and sizes in one masking means  30 . 
     The filaments  32 ,  34 ,  36  may be formed from metal materials, plastics, glass fibres, aramid fibres or carbon fibres, or else suitable material combinations such as insert-moulded steel cores or mesh materials. 
     As described above it is necessary to guide and to align the masking means  30  with respect to the semi-finished product  10  so as to assist the filaments  32 ,  34 ,  36  in resting on one another.  FIG. 4  and  FIG. 5  accordingly show two possible ways to guide or align the masking means  30  by a guide roller  42  or a centring strip  46 . 
       FIG. 4  accordingly illustrates a rotationally symmetrical guide roller with a centring means  44  in the form of a V-groove, and  FIG. 5  illustrates a fixed centring strip  46  with a centring means  44 , likewise in the form of a V-groove. 
     This ensures that, when the masking means  30  with a plurality of filaments  32 ,  34  is used according to the invention, alignment is possible on a filament which is annotated with the number  34  in the exemplary embodiments, which is used as a reference for alignment by means of the V-groove. The position of the masking means  30  is therefore unambiguously defined on the basis of the filament  34 . 
     According to the invention, the masking means  30  is prestressed. A force component which can additionally press the filament  34  against the semi-finished product  10  can now be produced particularly advantageously during alignment of the filaments  32 ,  34  by the centring means  44  with a V-groove on the filament  32 . 
     It is furthermore feasible, with a suitable configuration of the centring means  44 , for the exemplary configurations of the masking means  30   a ,  30   b  shown in  FIG. 3  or other suitable masking means configurations likewise to be aligned with respect to the semi-finished product with the aid of arrangements with guide rollers or centring strips. 
     It has been found that even a single filament on a rigid mount substrate makes it possible to ensure reliable shadowing, and therefore to prevent short circuits. The use of a filament consisting of a wire with a thickness of 50 micrometres, for example, on a mount substrate composed of glass resulted in sufficiently sharp shadowing. The wire with a diameter such as this is already sufficiently flexible to result in an area contact on a rigid mount substrate as well, thus ensuring reliable shadowing and preventing short circuits. 
       FIGS. 6 and 7  show a deposition chamber  70  with a hold-down device  80  for carrying out the method according to the invention. First of all, it should be mentioned that the curvature of the semi-finished product  10  is in this case illustrated in an exaggerated form, in order to assist understanding. 
     Semi-finished products  10  with rigid mount substrates are considered to be stiff and generally have high coefficients of elasticity. In consequence, only minor deformation can occur in order that critical stress characteristic values, for example the bending tensile strength in the case of glass materials, are not exceeded by the deformation process. 
     The semi-finished product  10  is arranged on a receptacle  76  and is curved in advance with respect to a deposition device  72 . This curvature can be produced by the natural weight of the semi-finished product  10  or by suitable means, for example by holders  62   a ,  62   b . The holders  62   a ,  62   b  can advantageously also be used to shadow edge areas of the semi-finished product  10  with respect to the deposition device  72 , in order to prevent material from being deposited in these areas, and therefore undesirable contacts being made. 
     A hold-down device  80  is arranged in the deposition chamber  70 , which hold-down device  80  has a masking device  60  with masking means  30  for partial shadowing and structuring of the surface  74  of the semi-finished product  10  with respect to the deposition device  72 . In order to guide the masking means  30 , guide rollers  42   a ,  42   b  are associated with them and are provided on frame parts  66   a ,  66   b  of the hold-down device. It is particularly advantageous for the guide rollers  42   a ,  42   b  to likewise be used to additionally prestress the masking means  30  with respect to the semi-finished product  10 . The masking means  30  are prestressed by stressing means  56  in the form of springs. In the illustrated example, the stressing means  56  are integrated directly in the masking means  30  although, nevertheless, other implementations are feasible, in which prestressing forces are introduced into the masking means  30  from the outside. 
     During the deposition process, the hold-down device  80  can now be used with the masking device  60  to ensure that the semi-finished product  10  is held exactly and securely on the receptacle  76 , and the material layer to be deposited is structured. 
       FIGS. 8 and 9  now show a subsequent method step. The masking means  30  is offset according to the invention in an offset chamber  84  with an offset device  86 , for example in order to produce a solar cell arrangement as shown in  FIG. 1  or  FIG. 2 .  FIG. 8  shows that the hold-down device  80  has now been lifted off the semi-finished product  10  by means of the masking device  60  with the masking means  30 , as indicated by the arrows  90   a ,  90   b . Lifting means  88   a ,  88   b , for example in the form of threaded spindles or pneumatic cylinders, are provided for this purpose. The semi-finished product  10  is also fixed by means of holders  62   a ,  62   b  on the receptacle  76 . 
     An offset can now be produced in this way, for example corresponding to the double-headed arrow annotated with the number  94  in  FIG. 9 . The offset movement is initiated via offset means  92   a ,  92   b  which are in turn in the form of threaded spindles or pneumatic cylinders. This results in a relative movement between the semi-finished product  10 , which is fixed on the receptacle  76 , and the offset device  86 . This is followed by a step in which the hold-down device  80  is lowered once again onto the surface  74  of the semi-finished product, in order to apply the masking means  30  and to allow a prestress to be produced with respect to the semi-finished product  10 . A further material layer to be structured and to be deposited can now be applied. 
     It is self-evident that the arrangements of the deposition chamber  76  shown in  FIG. 6  and of the offset chamber  84  shown in  FIG. 8  can be physically separated or else conversely combined. Both variants are feasible and are influenced, inter alia, by the planned throughput of the installation. 
       FIG. 10  shows another refinement of an offset chamber  84 .  FIG. 10   a  shows an arrangement in which the semi-finished product  10  is arranged on a cover-side receptacle  76 , and is held by means of the hold-down device  80  with the masking device  60 . At the bottom, fixing means  96   a ,  96   b ,  96   c  are provided, which have not yet engaged with the semi-finished product  10 . 
     In contrast,  FIG. 10   b  now shows a state in which the hold-down device  80  has been removed from the semi-finished product  10  by pivoting. The pivoting movement about a pivoting axis  100  is indicated by the arrow annotated with the number  102 . To do this, the fixing means  96   a ,  96   b ,  96   c  must secure the semi-finished product  10  against becoming loose from the receptacle  76 . The movement which takes place for this purpose is indicated by the arrows annotated  98   a ,  98   b  and  98   c . The offset movement of the masking device  60  can now be carried out, for example analogously to  FIG. 9 . 
       FIG. 11  shows an alternative configuration of a deposition chamber  76  with the semi-finished product  10  arranged as shown in  FIG. 10  on the receptacle  76  provided on the cover side. The deposition device  72  is arranged at the bottom. In this arrangement, the masking means  30  have and are held by buffer means  104   a ,  104   b  in the form of filament rollers. The guide rollers  42   a ,  42   b  are used to change the direction of the masking means and to apply a prestressing force in the direction of the surface  74  of the semi-finished product  10 . A prestressing force in the longitudinal direction of the masking means is introduced by a stressing means  56  in the form of a spring, which acts on the guide roller  42   b.    
     The masking means  30  particularly advantageously carries out a relative movement along its longitudinal direction with respect to the semi-finished product  10 , as indicated by the arrows annotated  105   a  and  105   b . This makes it possible to effectively reduce the deposition of material on the masking means  30 . In particular, this also makes it possible to move the masking means  30  continuously or quasi-continuously into a cleaning device, in order to allow material residues and other contamination relating to the process to be removed. 
     In this context, it should also be added that the filaments of the masking means  30  may already rest on one another on the buffer means  104   a ,  104   b , or else can each be fed in individually by a plurality of buffer means, resting on one another only by means of the guide rollers and centring means, in which case they can be separated again after passing the semi-finished product  10 , and can be wound up on separate buffer means. 
       FIGS. 12 and 13  show a flowchart for carrying out the method according to the invention by means of an apparatus  106  in the form of a cluster or cell manufacturing installation, and in this case the process procedure indicated by a process arrow sequence annotated  109 . A transport means  108  for feeding the semi-finished products  10 ,  10 ′,  10 ″ in and out is coupled to a lock  110  which is used to decouple the process gas atmosphere or the vacuum on the process side from the environment. 
     A handling chamber  122  with a handling device  124 , for example in the form of a handling robot, ensures handling of the semi-finished product  10 ′ in the apparatus  106 . It is feasible for the hold-down apparatus  80  to be applied to the semi-finished product  10 ′ with the masking device  60 , for example as shown in  FIG. 6  and  FIG. 7 , in the lock  110 . As is illustrated in  FIG. 12 , this allows the semi-finished product  10 ′ to be introduced into a first chamber  112  for deposition of the rear contact, and, immediately after this, to be introduced into a chamber  114  for deposition of the n-layer. 
     This is followed by a first offset process, which is carried out in the offset chamber  84 , which can be designed as shown in  FIG. 7  and, for example but not exclusively, can be provided with the offset device  86 . This is followed by a transfer into a chamber  116  for deposition of the i-layer, which is in turn followed by an offset process in the offset chamber  84 . A transfer then takes place to a chamber  118  for deposition of the p-layer and, finally, the transfer to a chamber  120  for deposition of the front contact. 
     After passing through the lock  110  again and being transferred from the process gas atmosphere or the vacuum on the process side to the environment, the semi-finished product  110 ″, which is now provided with a solar cell arrangement produced according to the invention, can once again be fed to the transport means  108 . 
     Semi-finished products  10  with rigid mount substrates are particularly suitable for producing large-area solar cell arrangements, since the mount substrates of the arrangement provide mechanical strength, thus allowing series-production-compatible handling of even relatively large units. The apparatus  106 , illustrated by way of example, for carrying out the method according to the invention makes it possible to process semi-finished products  10  with rigid mount substrates whose base areas cover approximately areas from less than 0.5 m 2  to more than 5 m 2 . These base areas are advantageously square or rectangular, but may also have other suitable shapes. 
     It is self-evident that further method steps can be carried out before, between, after or else at the same time as the method according to the invention in order to complete the production of solar cell arrangements. 
     In particular, these may be cutting and cleaning processes, the fitting of further active and passive components, test and inspection steps as well as lamination or assembly processes. An antireflective coating is furthermore normally applied to the surface of such solar cells, in order to optimize the effect of the incident light. 
       FIG. 14  finally schematically illustrates one possible procedure for the method according to the invention, which can be carried out using an apparatus as shown in  FIG. 12  and  FIG. 13 . 
     Alternatively, it is feasible to use the process steps in  FIG. 14  to carry out production-line or conveyor belt production, which can be advantageous, for example, when mass production is planned. Two locks  110   a ,  110   b  can accordingly be provided on the basis of the illustrated process, one of which is used for the inlet to and the other for the outlet from the process gas atmosphere or the process-dependent vacuum. Process chambers  112 ,  114 ,  116 ,  118  and  120  for deposition of material layers are arranged in between and two offset chambers  84   a ,  84   b  for offsetting the masking means  30  are in turn connected between them. The necessary transfer takes place by means of the handling device  124 , which is indicated by arrows here. 
     It should also be added that mixed forms such as a combined production line and cell manufacture are also feasible, particularly when it appears to be possible for a plurality of lines to use expensive manufacturing facilities or else to create buffer options for process protection. 
     The method according to the invention now makes it possible to produce series-connected thin-film solar cells with rigid mount substrates in a simple and advantageous manner. In particular, the method steps involved in the connection process are carried out in the process gas atmosphere or in the vacuum, without the structuring of the material layers that is required in this case having to be provided on the outside. 
     This in-situ connection allows expenditure for external apparatuses such as laser cutting installations or mechanical scoring installations to be avoided or reduced. Furthermore, the process quality is improved because fewer lock processes and fewer transfer processes are now required outside the process gas atmosphere or the vacuum.