Patent ID: 12224364

LIST OF REFERENCE CHARACTERS

1thin-film solar module2first substrate3layer structure4module surface5rear electrode layer5-1,5-2,5-3rear electrode layer section6absorber layer7buffer layer8front electrode layer8-3front electrode layer section9adhesive layer10second substrate11solar cell12composite13connection section14patterning zone15bulge16layer region17dead zone18optically transparent zone19decoating region20electrode zone21edge zone22zone region22-1,22-2zone region portion

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG.1schematically illustrates a thin-film solar module according to the present invention referenced as a whole with the number1using a cross-sectional view. The thin-film solar module1comprises a plurality of solar cells11serially connected one to another in integrated form, wherein in a greatly simplified manner only two solar cells11are depicted. Of course, generally speaking, in the thin-film solar module1, a large number of solar cells11(for example, approximately 100-150) are serially connected.

The thin-film solar module1has a composite pane structure in substrate configuration, in other words, it has a first substrate2with a layer structure3made of thin films applied thereon, wherein the layer structure3is arranged on a light-entry side surface of the first substrate2. Here, the first substrate2is implemented, for example, as a rigid glass plate with relatively high light transmittance, while other electrically insulating materials with desired stability and inert behavior relative to the process steps carried out can equally be used.

The layer structure3includes, arranged on the light-entry side surface of the first substrate2, an opaque rear electrode layer5, which is made, for example, from a light-impermeable metal such as molybdenum (Mo) and was applied on the first substrate2by vapor deposition or magnetron-enhanced cathodic sputtering (sputtering). The rear electrode layer5has, for example, a layer thickness in the range from 300 nm to 600 nm.

A photovoltaically active (opaque) absorber layer6that is made of a semiconductor doped with metal ions whose bandgap is capable of absorbing the greatest possible share of sunlight is applied on the rear electrode layer5. The absorber layer6is made, for example, of a p-conductive chalcopyrite compound semiconductor, for example, a compound of the group Cu(In/Ga)(S/Se)2, in particular sodium (Na)-doped Cu(In/Ga)(S/Se)2. The preceding formulas are understood to mean that indium (In) or gallium (Ga) as well as sulfur (S) or selenium (Se) can be present alternatively or in combination. The absorber layer6has a layer thickness that is, for example, in the range from 1 to 5 μm and is, in particular, approx. 2 μm. Typically, for the production of the absorber layer6, various material layers are applied, for example, by sputtering, and are subsequently thermally converted to form the compound semiconductor by heating in a furnace (RTP=rapid thermal processing), optionally, in an atmosphere containing S- and/or Se. This manner of production of a compound semiconductor is well known to the person skilled in the art such that it need not be discussed in detail here.

Deposited on the absorber layer6is a buffer layer7, which consists here, for example, of a single layer of cadmium sulfide (CdS) and a single layer of intrinsic zinc oxide (i-ZnO), not depicted in detail inFIG.1.

A front electrode layer8is applied on the buffer layer7, for example, by sputtering. The front electrode layer8is transparent to radiation in the visible spectral range (“window electrode”) such that the incoming sunlight (depicted inFIG.1by four parallel arrows) is weakened only slightly. The front electrode layer8is based, for example, on a doped metal oxide, for example, n-conductive aluminum (Al)-doped zinc oxide (ZnO). Such a front electrode layer8is generally referred to as a TCO layer (TCO=transparent conductive oxide). The layer thickness of the front electrode layer8is, for example, approx. 500 nm. A heterojunction (i.e., a sequence of layers of opposing conductor type) is formed by the front electrode layer8together with the buffer layer7and the absorber layer6. The buffer layer7can effect electronic adaptation between the absorber layer6and the front electrode layer8.

For the formation and serial connection of the solar cells11, the layer structure3was patterned using suitable patterning technology, for example, laser lithography and/or mechanical removal. Typically, a plurality of immediate sequences of three patterning lines P1-P2-P3 in each case in the form of layer ditches are introduced into the layer structure3in this order. Here, at least the rear electrode5is subdivided by first patterning lines P1; at least the absorber layer, by second patterning lines P2; and at least the front electrode layer8, by third patterning lines P3 by production of respective ditches. Via the second patterning lines P2, the front electrode layer8of one solar cell11is in each case electrically conductively connected to the rear electrode layer5of an adjacent solar cell11, with the front electrode layer8directly contacting the rear electrode layer5, for example. In the exemplary embodiment depicted, the ditches of the first patterning lines P1 are filled by material of the absorber layer6. The ditches of the second patterning lines P2 are filled by material of the front electrode layer8, and the ditches of the third patterning lines P3 are filled by the adhesive layer9mentioned in the following. Each immediate sequence of a first, second, and third patterning line P1-P2-P3 forms a patterning zone14. InFIG.1, by way of example, only a single patterning zone14is depicted, by means of which the serial connection of two adjacent solar cells11is defined, wherein it is understood that in the thin-film solar module1, a large number of such patterning zones14are provided for the patterning and serial connection of solar cells11.

In the exemplary embodiment depicted here, both the positive power connector (+) and the negative power connector (−) of the thin-film solar module1are routed via the rear electrode layer5and electrically contacted there. For this purpose, the layers of the layer structure3are removed all the way to the rear electrode layer5in the two peripheral connection sections13of the thin-film solar module1.

For protection against environmental influences, a (plastic) adhesive layer9that serves to encapsulate the layer structure3is applied on the front electrode layer8. Adhesively bonded with the adhesive layer9is a second substrate10transparent to sunlight that is implemented, for example, in the form of a glass sheet made of extra white glass with a low iron content, with the equally possible use of other electrically insulating materials with desired strength and inert behavior relative to the process steps carried out. The second substrate10serves for the sealing and for the mechanical protection of the layer structure3. The thin-film solar module1can absorb light via the front-side module surface4of the second substrate10in order to produce an electrical voltage on the two power connectors (+, —). A resulting current path is depicted inFIG.1by serially arranged arrows.

The two substrates2,10are fixedly bonded (“laminated”) to one another via the adhesive layer9, with the adhesive layer9implemented here, for example, as a thermoplastic adhesive layer, which can be reshaped plastically by heating and which fixedly bonds the two substrates2,10to one another during cooling. The adhesive layer9is made here, for example, of PVB. Together, the two substrates2,10with the solar cells11embedded in the adhesive layer9form a laminated composite12.

Reference is now made toFIG.2A-2D, wherein exemplary embodiments of the patterning zone14of the thin-film solar module1according to the invention are depicted schematically in plan view.FIG.2A-2Ddepict in each case only one single patterning zone14, while the thin-film solar module1typically has a large number of patterning zones14(e.g., approx. 100). The patterning zones14form in each case a photovoltaically inactive dead zone17that can make no contribution to energy production.

The patterning zones14are in each case arranged parallel to the module edge, here, for example, in x-direction, which can also be referred to as the width of the thin-film solar module1. The y-direction perpendicular thereto can be referred to as the length of the thin-film solar module1. The peripheral connection sections13depicted inFIG.1are not shown inFIG.2A-2D. The two connection sections13also form in each case a photovoltaically inactive dead zone that can make no contribution to energy production.

Situated on both sides adjacent a patterning zone14is, in each case, a layer region16that represents, in the context of the present invention, a solar cell11with an optically active zone. In the inner region of the thin-film solar module1, each layer region16is arranged between two immediately adjacent patterning zones14and is delimited thereby. In the case of the two peripheral solar cells11, the layer region16is, in each case, arranged between a patterning zone14and the adjacent connector section13shown inFIG.1and is delimited thereby. The layer region16comprises in each case a section of the rear electrode layer5, absorber layer6, buffer layer7and front electrode layer8, which are the rear electrode, absorber, and front electrode of the solar cell11.

The patterning zones14ofFIG.2A-2Dhave in each case, in a zone region22reduced by the first patterning line P1 (without first patterning line P1), a plurality of optically transparent zones18, which are here arranged, for example, linearly in x-direction and parallel to the patterning lines P1-P3. Here, it is essential that the optically transparent zones18are implemented such that the rear electrode layer5is (areally) continuous in the zone region22of the patterning zone14, i.e., is not completely subdivided into sections spatially separated from one another. The optically transparent zones18have each case a square shape. However, in principle, the transparent zones18can have any shape, for example, linear, punctiform, or circular disc-shaped. Each optically transparent zone18is surrounded by an edge zone21.

The structure of an optically transparent zone18and edge zone21is illustrated inFIGS.3and4, whereinFIG.4, which is a cross-sectional view ofFIG.3along the section line A-A, shows the layer sequence. Accordingly, the optically transparent zone18is, for achieving the desired optical transparency of the thin-film solar module1, rear-electrode-layer-free and preferably also absorber-layer-free, but can, however, for example, have a front electrode layer section, which is not shown inFIGS.3and4. As shown inFIG.4, in the optically transparent zone18, for example, all layers of the layer structure3are removed all the way to the substrate2(in other words, rear electrode layer5, absorber layer6, buffer layer7, and front electrode layer8). However, it is also possible that not all layers of the layer structure3are removed in the optically transparent zone18, with, in any case, the generally opaque rear electrode layer5removed.

The optically transparent zone18is surrounded by an edge zone21. In the edge zone21, all layers are removed, with the exception of a rear electrode layer section5-3. By means of the edge zone21, short-circuit current paths on the edges of the decoated areas can advantageously be avoided. Advantageously, the ratio of the total area of the optically transparent zones18to the total area of the edge zones21is greater than 1, preferably greater than 10.

Reference is now made again toFIG.2A-2D. The various embodiments of the patterning zones14inFIG.2A-2Ddiffer as follows:

InFIG.2A, the patterning zone14comprises one first patterning line P1, one second patterning line P2, and two third patterning lines P3 and P3′. The outwardly positioned third patterning line P3′ is provided with a plurality of square-shaped bulges15, in which, in each case, an optically transparent zone18is arranged. The bulges15of the third patterning line P3 bulge in each case in a direction away from the first patterning line P1 (i.e., in the positive y-direction).

In contrast thereto, inFIG.2B, the patterning zone14comprises one first patterning line P1, one second patterning line P2, and only one third patterning line P3. Analogously toFIG.2A, the third patterning line P3 is provided with a plurality of square-shaped bulges15in which, in each case, an optically transparent zone18is arranged.

InFIG.2C, the patterning zone14comprises one first patterning line P1, one second patterning line P2, and one third patterning line P3. The third patterning line P3 is provided with a plurality of square-shaped bulges15in the positive y-direction, in which, in each case, an optically transparent zone18is arranged. In addition, the first patterning line P1 is provided with a plurality of square-shaped bulges15in the negative y-direction, in which, in each case, an optically transparent zone18is arranged. The bulges15of the third patterning line P3 and the bulges15of the first patterning line P1 are positioned opposite one another.

The embodiment of the patterning zone14ofFIG.2Ddiffers from the embodiment ofFIG.2Conly in that the second patterning line P2 is not continuous in the region between the bulges15, but is, instead, interrupted. The two optically transparent zones18, which are arranged in the bulge15of the first patterning line P1 and in the bulge15of the third patterning line P3, are combined to form a common optically transparent zone18.

Reference is now made toFIG.5A-5C, wherein additional exemplary embodiments of the patterning zone14of the thin-film solar module1according to the invention are illustrated schematically in plan view. Accordingly, the patterning zone14comprises at least one linear decoating region19, which extends parallel to the patterning lines P1-P2-P3, i.e., in x-direction, continuously over the full dimension of the patterning zone14. Advantageously, all patterning zones14of the thin-film solar module1have one or more linear decoating regions19. The linear decoating region19is in each case arranged in a zone region22reduced by the first patterning line P1, i.e., in a remaining region of the patterning zone14without the first patterning line P1. By means of the linear decoating region19, the zone region22is subdivided into two zone region portions22-1,22-2. One zone region portion22-1includes a rear electrode layer section5-1; the other zone region portion22-2includes a rear electrode layer section5-2different therefrom.

Each linear decoating region19is composed of a plurality of optically transparent zones18and a plurality of electrodes zones20in alternating sequence, in other words, one optically transparent zone18is situated between two electrodes zones20and/or one electrode zone20is situated between two optically transparent zones18. The optically transparent zones18and electrode zones20have a structure as it has already been described in conjunction withFIGS.3and4. The electrode zones20are sections of the edge zone21surrounding the optically transparent zone18, which sections are positioned opposite one another. Accordingly, the layer sequence in the electrode zones20corresponds to that of the edge zone21such that, in the electrode zones20, all layers with the exception of a rear electrode layer section5-3are removed. The electrode zones20can in each case also have a front electrode layer section8-3.

As illustrated inFIG.5A-5D, the electrode zones20are those sections of the edge zone21that completely bridge the linear decoating region19(perpendicular to the extension direction of the patterning zone14) in y-direction. Here, each electrode zone20is, for example, rectangular. The spatially separated from one another rear electrode layer sections5-1,5-2of the two zone region portions22-1,22-2are areally connected to one another such that the rear electrode layer5of the zone region22of the patterning zone14is areally continuous. The two zone region portions22-1,22-2are directly connected electrically to one another in series via the rear electrode layer sections5-3of the electrode zones20. Of course, the rear electrode layer sections5-1,5-2of the two zone region portions22-1,22-2of one and the same zone region22can be areally connected to one another by one or more electrodes zones20. It is equally conceivable for the linear decoating region19not to be parallel to the patterning zone14but, rather, aligned obliquely at an angle other than 0° relative to the patterning zone14.

In the thin-film solar module1according to the invention, the solar cells11are opaque and have transmittance for visible light of less than 5%. In contrast to this, the optically transparent zones18have transmittance for visible light of at least 85%. The ratio of the total area of all optically transparent zones18to the total area of the solar cells11is in the range from 5% to 50%. Thus, the optical transparency of the semitransparent thin-film solar module averaged over the total area of the thin-film solar module1is also in the range from 5% to 50% and is, in particular, 20%. The optically transparent zones18are arranged uniformly distributed along the linear decoating region19, by which means a very smooth overall visual effect can be obtained.

InFIG.5A, the linear decoating region19is arranged between the first patterning line P1 and the second patterning line P2 of the patterning zone14. InFIG.5B, the linear decoating region19is arranged between the second patterning line P2 and the third patterning line P3 of the patterning zone14. InFIG.5C, the linear decoating region19is arranged between the first patterning line P1 and the third patterning line P3 and forms the (single) second patterning line P2 of the patterning zone14. Thus, the formation of a separate second patterning line P2 can be dispensed with.

In the two embodiments ofFIGS.5A and5B, it would be possible for the electrode zones20to have, in each case, no front electrode layer section8-3. For the embodiment ofFIG.5C, it is, however, necessary for at least one electrode zone20, in particular all electrode zones20, to have a front electrode layer section8-3, since due to the function as a second patterning line P2, a serial connection of the solar cells11adjacent the patterning zone14must be enabled.

InFIG.6A through6C, by way of example, additional embodiments of the patterning zone14of the thin-film solar module according to the invention are in each case schematically depicted in plan view. To avoid unnecessary repetition, only the differences relative to the embodiments ofFIG.5A through5Care explained and, otherwise, reference is made to the statements there. In the embodiments ofFIG.6A through6C, the electrode zones20have in each case no front electrode layer section8-3.

In the embodiment ofFIG.6A, the patterning zone14has, in addition to a first patterning line P1 and a second patterning line P2, two third patterning lines P3 and P3′ positioned near one another, with the patterning line P3′ positioned farther outward compared to the patterning line P3 being formed by the linear decoating region19.

In the embodiment ofFIG.6B, the patterning zone14has, in addition to a first patterning line P1 and a second patterning line P2, a single third patterning line P3, with the third patterning line P3 being formed by the linear decoating region19.

In the embodiment ofFIG.6C, the patterning zone14has, in addition to a first patterning line P1 and a second patterning line P2, two third patterning lines P3 and P3′ positioned near one another, with the linear decoating region19arranged between the two third patterning lines P3 and P3′.

FIGS.7A and7Bschematically depict in each case cross-sectional views of an embodiment of the patterning zone14according to the invention.

InFIG.7A, the layer structure3applied on the substrate2comprises an opaque rear electrode layer5, an absorber layer6, and a front electrode layer8. In the layer structure ofFIG.7B, a buffer layer7is additionally provided. The layer structure is patterned in each case by a first patterning line P1, a second patterning line P2, and a third patterning line P3. An optically transparent zone18, in which the rear electrode layer5is removed, is arranged between the first patterning line P1 and the second patterning line P2, corresponding to the embodiment ofFIG.5A. InFIG.7A, the first patterning line P1 is filled by material of the absorber layer6, and the optically transparent zone18is filled by the material of the front electrode layer8. Formation of the optically transparent zone18is done after depositing the absorber layer6and before depositing the front electrode layer8. InFIG.7B, both the first patterning line P1 and the optically transparent zone18are filled by the material of the buffer layer7, with formation of the optically transparent zone18done before depositing the buffer layer7and the front electrode layer8.

FIG.8illustrates an exemplary method for producing the thin-film solar module1according to the invention.

According to it, in step I, a substrate2with a layer structure3with patterning zones14introduced therein for the formation of serially connected solar cells11is provided.

In step II, the optically transparent zones18are produced by removal of all layers of the layer structure3all the way to the substrate2using a pulsed laser beam of a laser beam source. For this purpose, the layer structure3is irradiated with a pulsed laser beam, with pulses having a duration of less than 1 nanosecond. The layer structure3is preferably irradiated through the transparent substrate2; however, direct irradiation of the layer structure3from the side facing away from the substrate2is also possible. Alternatively, the optically transparent zones18can be produced by mechanical material removal. The optically transparent zones18are respectively produced in the zone regions22reduced by the first patterning line P1 such that the rear electrode layer5in the zone regions22is in each case continuous.

In an optional step III, edge zones21are produced around the optically transparent zones18. The edge zones21are produced by irradiation of the layer structure3with a pulsed laser beam, with the pulses having a duration of less than 1 nanosecond, and/or by mechanical material removal. When edge zones21are produced around the optically transparent zones18, it is possible to also produce the optically transparent zones18by irradiation with a pulsed laser, whose pulses have a duration of at least 1 nanosecond.

The invention advantageously makes available a semitransparent thin-film solar module. The patterning zones of the solar cells have optically transparent zones and are, in particular, subdivided by linear decoating regions, wherein each linear decoating region has optically transparent zones and electrode zones in an alternating sequence. The patterning zones have, in a zone region reduced by the first patterning line (without first patterning line), a continuous rear electrode layer.

As is evident from the above description, the invention advantageously enables technically relatively uncomplicated, highly versatile, and economical production of the thin-film solar module, wherein a relatively large optically active area with comparatively high visible-light transmittance of the thin-film solar module can be obtained.