THIN FILM SOLAR MODULE AND PRODUCTION METHOD

Abstract

The invention relates to a thin film solar module comprising a monolithic solar cell array (1), including a plurality of solar cells (2) with a layer structure, comprising a rear contact layer (3), a front contact layer (4) and an absorber layer between the rear contact layer and the front contact layer, and an electrical connection structure (6) for electrically serially connecting neighbouring solar cells. The invention also relates to an associated production method. In the thin film solar module according to the invention, the electrical connection structure includes contact strips (7) for electrically serially connecting neighbouring solar cells, wherein the electrical connection structure electrically serially connects two respective solar cells (2.sub.m, 2.sub.m.sub.+1) that are adjacent to one another in a series connection direction (RS) via one or more contact strips (7). The contact strips run spaced apart from one another and transverse to the series connection direction with a direction component in the series connection direction in connection strip regions (8) of the solar cells. Each contact strip contacts a side (3a) of the rear contact layer of the one solar cell facing an absorber layer and a side (4b) of the front contact layer of the other solar cell facing away from an absorber layer, wherein the connection strip regions of the solar cells have connection recesses (9) in the front contact layer and the absorber layer for exposing the side of the rear contact layer facing the absorber layer. The invention also relates to the use of same in thin film solar cell technology.

Claims

1. A thin film solar module having a monolithic solar cell array, which includes a plurality of solar cells having a layered structure that has a rear contact layer, a front contact layer, and an absorber layer between the rear contact layer and the front contact layer; and an electrical connection structure having contact strips for electrically connecting in series solar cells arranged adjacent to one another, wherein the electrical connection structure electrically connects in series each two solar cells (2.sub.m, 2.sub.m.sub.+1) adjoining in a series connection direction by one or more contact strips; wherein the contact strips are spaced apart from one another transversely to the series connection direction and extend with a directional component in the series connection direction in connecting strip regions of the solar cells and each contact strip contacts a side of the rear contact layer of one of the solar cells facing toward the absorber layer and a side of the front contact layer of the other solar cell facing away from the absorber layer, wherein the connecting strip regions of the solar cells have connecting openings in the front contact layer and the absorber layer to expose the side of the rear contact layer facing toward the absorber layer; and wherein the respective contact strip extends in the connecting strip region in a connecting trench of the other solar cell that forms the connecting opening and contacts the rear contact layer of the relevant solar cell continuously along its extension over the rear contact layer and extends between the associated solar cells over a separating strip region separating them, with an insulating layer interposed, and wherein the respective contact strip is attached as a prefabricated wire or tape material and/or its contact surface to the rear contact layer has a length/width ratio of at least 3:1; or wherein the respective contact strip extends in the connecting strip region with an insulating layer interposed on the front contact layer of the relevant solar cell and contacts the rear contact layer of the relevant solar cell along its extension in one or more contact sections spaced apart from one another, in which the connecting opening in the connecting strip region forms a via opening in each case.

2. The thin film solar module of claim 1, wherein a cell width of the respective solar cell in the series connection direction is at least 2 cm to at least 3 cm; and the efficiency of the thin film solar module is at least 14% to at least 16% and/or a maximum of the efficiency of the thin film solar module as a function of a cell width of the respective solar cell in the series connection direction is in a range of the cell width between 2 cm and 10 cm, and/or the efficiency of the thin film solar module as a function of the cell width of the respective solar cell in the series connection direction varies in the range of the cell width between 2 cm and 20 cm by at most 10% to 20% in relative terms.

3. The thin film solar module of claim 1, wherein a first (2.sub.m.sub.-1) and a third solar cell (2.sub.m.sub.+1) adjoin a second solar cell (2.sub.m) on opposite sides, wherein the first and the second solar cell are electrically serially connected by one or more first contact strips and the second and the third solar cell are electrically serially connected by one or more second contact strips and each of the first contact strips contacts the side of the rear contact layer of the first solar cell facing toward the absorber layer and the side of the front contact layer of the second solar cell facing away from the absorber layer, and each of the second contact strips contacts the side of the rear contact layer of the second solar cell facing toward the absorber layer and the side of the front contact layer of the third solar cell facing away from the absorber layer, and wherein, in the region of the second solar cell, at least one first and one second contact strip extend overlapping in the direction transverse to the series connection direction.

4. The thin film solar module of claim 3, wherein, in the region of a respective solar cell, the first contact strips are arranged at equal transverse distance from one another and/or the second contact strips are arranged at equal transverse distance from one another and/or the first and the second contact strips are arranged alternating at equal transverse distance from one another.

5. The thin film solar module of claim 4, wherein the transverse distance of the first contact strips from one another is between 10 mm and 100 mm; and/or the transverse distance of the second contact strips from one another is between 10 mm and 100 mm; and/or the transverse distance of the first and second contact strips from one another is between 5 mm and 50 mm.

6. The thin film solar module of claim 1, wherein the solar cell array has a substrate layer on which the solar cells are arranged jointly with their rear contact layer facing toward the substrate layer, wherein each two adjacent and electrically serially connected solar cells are separated from one another in their layer structure by a separating strip region and the contact strips extend beyond their separating strip region for the electrical series connection of the two solar cells.

7. The thin film solar module of claim 1, wherein the contact strips are components that are manufactured separately from the monolithic solar cell array and attached to the monolithic solar cell array.

8. The thin film solar module of claim 1, wherein the contact strips extend in the region of a respective solar cell with a strip length that is at least 50% to at least 80% of the longitudinal extension of the solar cell in the extension direction of the contact strips; and/or the contact strips extend in the region of a respective solar cell with their strip section contacting the front contact layer having a strip length that is less than the longitudinal extension of the solar cell in the extension direction of the contact strips by a shortening distance that is at most twice as large or at most as large as a grid spacing of a contact grid structure of the front contact layer.

9. The thin film solar module of claim 8, wherein the longitudinal extension of the respective solar cell in the extension direction of the contact strips is between 10 mm and 300 mm.

10. A method for producing a thin film solar module, having the following steps: prefabricating a monolithic solar cell array comprising a plurality of solar cells, a rear contact layer, a front contact layer, and an absorber layer between the front contact layer and the rear contact layer; forming connecting openings on connecting strip regions of the solar cells; attaching contact strips in the connecting strip regions with electrical contacting with the rear contact layer in the connecting openings and with the front contact layer of the respective associated solar cells; and completing the thin film solar module panel.

11. The method of claim 10, wherein an insulating layer is applied in the connecting strip regions on the front contact layer and/or inseparating strip regions before the contact strips are attached.

Description

[0033] Advantageous embodiments of the invention are shown in the drawings. These and further advantageous embodiments of the invention are described in more detail hereinafter. In the figures:

[0034] FIG. 1 shows a top view of a thin film solar module having twenty serially connected solar cells in two rows,

[0035] FIG. 2 shows a top view of a thin film solar module having forty serially connected solar cells in four rows,

[0036] FIG. 3 shows a top view of a thin film solar module having sixty serially connected solar cells in six rows,

[0037] FIG. 4 a detailed view of a region IV in FIG. 3,

[0038] FIG. 5 shows a detailed top view of a thin film solar module of the type from FIGS. 1 to 3 in an embodiment having continuous contacting of contact strips with a rear contact layer,

[0039] FIG. 6 shows the view from FIG. 5 for an embodiment with punctiform contacting of the contact strips with the rear contact layer,

[0040] FIG. 7 shows a sectional view along a line VII-VII in FIG. 5,

[0041] FIG. 8 shows a sectional view along a line VIII-VIII in FIG. 6

[0042] FIG. 9 shows a sectional view along a line IX-IX in FIG. 5,

[0043] FIG. 10 shows a sectional view along a line X-X in FIG. 5,

[0044] FIG. 11 shows a sectional view along a line XI-XI in FIG. 5,

[0045] FIG. 12 shows a sectional view along a line XII-XII in FIG. 5,

[0046] FIG. 13 shows a sectional view along a line XIII-XIII in FIG. 6,

[0047] FIG. 14 shows a sectional view along a line XIV-XIV in FIG. 6,

[0048] FIG. 15 shows a sectional view along a line XV-XV in FIG. 6,

[0049] FIG. 16 shows a sectional view along a line XVI-XVI in FIG. 6, and

[0050] FIG. 17 shows a diagram of the module efficiency as a function of the cell width for an exemplary module design.

[0051] The thin film solar module shown in the figures in different embodiment variants comprises a monolithic solar cell array 1, which includes a plurality of solar cells 2 having a layered structure that has a rear contact layer 3, a front contact layer 4, and an absorber layer 5 between the rear contact layer 3 and the front contact layer 4. Furthermore, the thin film solar module includes an electrical connection structure 6 having contact strips 7 for electrically connecting in series solar cells arranged adjacent to one another, wherein the electrical connection structure electrically connects in series each two solar cells 2.sub.m.sub.-1 and 2.sub.m, 2.sub.m and 2.sub.m.sub.+1 etc. adjoining in a series connection direction RS by one or, as shown, multiple of the contact strips 7.

[0052] The monolithic solar cell array 1 is divided into the individual solar cells 2 in a manner known per se by means of separating strip regions 12. FIG. 1 illustrates an example in which the solar cell array 1 has a rectangular shape and is divided into two rows of ten solar cells 2.sub.1 to 2.sub.10 and 2.sub.11 to 2.sub.20 each, wherein the solar cells in each row are arranged adjacent to one another or successively in the mentioned series connection direction RS and are electrically connected in series. In the example shown, the solar cells 2.sub.1 to 2.sub.10 or 2.sub.11 to 2.sub.20 all have an equal cell width ZB, i.e., longitudinal extension in the series connection direction RS, wherein the cell width ZB can be in the range between 1 cm and 30 cm, in particular in the range between approximately 2 cm and approximately 10 cm. The two rows of solar cells are electrically connected to one another in series via a lateral busbar 18, and a connection socket unit 15 and two connection bars 16a, 16b are located on an opposite array side, also in a conventional manner. FIG. 2 similarly illustrates an example having four series-connected rows of ten series-connected solar cells 2.sub.1 to 2.sub.10, 2.sub.11 to 2.sub.20, 2.sub.21 to 2.sub.30, 2.sub.31 to 2.sub.40 each, wherein in this case three lateral busbars 18a, 18b, 18c ensure the series connection of the solar cell rows. FIG. 3 illustrates an example having six series-connected rows of ten series-connected solar cells 2.sub.1 bis 2.sub.10, ..., 2.sub.51 bis 2.sub.60 each, correspondingly using five busbars 18a to 18e for the series connection of the solar cell rows to one another. In the examples shown, the solar cell array 1 is rectangular, in alternative embodiments it has a different conventional shape. In the rectangular shape of the solar cell array 1 shown, the separating strip regions 12 preferably extend in a grid pattern, so that the solar cell array 1 is divided into rows and columns of solar cells. The series connection direction RS accordingly runs in the row or column direction.

[0053] The contact strips 7 are spaced apart from one another transversely to the series connection direction RS and extend with a directional component in the series connection direction RS in connecting strip regions 8 of the solar cells 2. Each contact strip 7 contacts a side 3a of the rear contact layer 3 of one of the solar cells 2 facing toward the absorber layer 5 and a side 4b of the front contact layer 4 of an adjacent other one of the solar cells 2 facing away from the absorber layer 5, wherein the connecting strip regions 8 of the solar cells have connecting openings 9 in the front contact layer 4 and the absorber layer 5 to expose the side 3a of the rear contact layer 3 facing toward the absorber layer.

[0054] In an embodiment illustrated in FIGS. 5, 7, and 9 to 12, the respective contact strip 7 continuously contacts the rear contact layer 3 of the relevant solar cell 2 along its extension above the rear contact layer 3. For this purpose, the respective connection recess 9 consists of a one-piece continuous connecting trench 9b in this case. A contact surface of the respective contact strip 7 to the rear contact layer 3 preferably has a length/width ratio of at least 3:1, for example at least 5:1 or at least 10:1 or at least 30:1 or at least 1000:1. For example, the contact strips 7 can have a length between approximately 1 cm and approximately 20 cm and a width between approximately 10 .Math.m and 3000 .Math.m. The respective connecting trench 9b can be dimensioned analogously, for example having a length/width ratio of at least 3:1, preferably at least 5:1 or at least 10:1 or at least 30:1 or at least 1000:1.

[0055] In an embodiment illustrated in FIGS. 6, 8, and 13 to 16, the respective contact strip 7 contacts the rear contact layer 3 of the relevant solar cell 2 along its extension over the rear contact layer 3 in one or, as shown, multiple contact sections 14 spaced apart from one another. These contact sections 14 are formed by corresponding via openings 9a in the front contact layer 4 and the absorber layer 5. In this case, the respective connecting opening 9 consists of one or, as shown, multiple of these via openings 9a in the relevant connecting strip region 8. In this case as well, the respective contact strip 7 can have, for example, a length of between approximately 1 cm and approximately 30 cm and a width between approximately 10 .Math.m and approximately 3000 .Math.m or a length/width ratio of at least approximately 3:1, for example, at least approximately 5:1 or at least approximately 10:1 or at least approximately 30:1 or at least 1000:1.

[0056] In corresponding implementations, as in the examples shown, the solar cell array 1 has a substrate layer 15 on which the solar cells 2 are jointly arranged, wherein their rear contact layer 3 faces toward the substrate layer 15, especially with a side 3b of the rear contact layer 3 facing away from the absorber layer 5. The substrate layer 15 can be, for example, a typical glass substrate, i.e., glass support, or any other conventional substrate known to those skilled in the art for supporting the solar cell thin film structure.

[0057] Each two adjacent and electrically serially connected solar cells 2.sub.m.sub.-1 and 2.sub.m, 2.sub.m, and 2.sub.m.sub.+1 etc. are separated from each other in their layer structure by the separating strip region 12, and the contact strips 7 extend for the electrical serial connection of the respective two solar cells 2m.sub.-1,2m etc. transversely over their separating strip region 12. In the embodiment of FIGS. 5, 7, and 9 to 12, the separating strip regions 12 are covered by an insulating layer 17 made of electrically insulating material, so that the crossing contact strips 7 do not come into contact there with side flanks of the rear contact layer 3 and the absorber layer 5 that are otherwise exposed there. The insulating layer 17 can be implemented by a conventional layer deposition technology or as a paste material incorporated in or applied to the separating strip regions 12 or prefabricated strip or tape material. In embodiments in which, as in the examples shown, the insulating layer 17 extends not only in the separating strip region 12 itself, but also in an adjacent region of the layer structure of absorber layer 5 and front contact layer 4, the insulating layer 17 is expediently made of a transparent material, i.e., a material that is transparent to light, which is relevant to the photovoltaic function of the solar cells 2 in the present case.

[0058] In the embodiment variant in which the respective contact strip 7 contacts the rear contact layer 3 of the solar cell 2 only in a quasi-punctiform manner in the one or more contact sections 14 spaced apart from one another to form corresponding contact pads or contact points, the insulating layer 17 is provided between the contact sections 14 in the connecting strip regions 8 between the front contact layer 4 and the contact strip 7 in order to keep the contact strip 7 electrically insulated from the front contact layer 4 in this region. The insulating layer 17 can in turn be provided in a layer deposition process or alternatively by a paste material or a prefabricated electrically insulating strip/tape material. In an advantageous manufacturing variant, the insulating layer 17 can be applied or attached continuously over the front contact layer 4 in the connecting strip region 8 of the relevant solar cell 2, after which via openings 9a are introduced into the insulating layer 17 in the region of the contact sections 14, as can be seen in FIG. 8. In any case, it is expedient in this case to use a light-transparent material for the insulating layer 17 in order to avoid corresponding light losses through the insulating layer 17 even in regions in which the insulating layer 17 is not covered by the contact strip 7, if for example, as in the example shown in the connecting strip region 8, it extends laterally beyond each of the applied contact strips 7 on the front contact layer 4.

[0059] In corresponding embodiments, the contact strips 7 are components that are manufactured separately from the monolithic solar cell array 1 and attached to the monolithic solar cell array 1. For this purpose, the contact strips 7 can be prefabricated, for example, as corresponding contact wires or contact tapes, as already mentioned above. Alternatively, the contact strips 7 are formed by a screen printing process from a suitable electrically conductive paste material with a subsequent drying or firing process, or by a layer deposition process in which a corresponding electrically conductive material is applied as a layer, after which this layer is structured into the contact strips 7, for example by typical photolithographic and etching processes. Numerous, preferably metallic materials are suitable for the contact strips 7, such as copper (Cu), for example as an optionally tinned strip material, silver (Ag), gold (Au), aluminum (Al), nickel (Ni), and alloys made up of several of these and/or other metals.

[0060] In advantageous embodiments, as in the example shown, a first solar cell 2.sub.m.sub.-1 and a third solar cell 2.sub.m.sub.+1 adjoin a second solar cell 2.sub.m on opposite sides, wherein the first solar cell 2.sub.m.sub.-1 and the second solar cell 2.sub.m are electrically connected in series by one or alternatively, as shown, multiple first contact strips 7a and the second solar cell 2.sub.m and the third solar cell 2.sub.m.sub.+1 are electrically connected in series by one or, as shown, multiple second contact strips 7b. Each first contact strip 7a contacts the side 3a of the rear contact layer 3 of the first solar cell 2.sub.m.sub.-1 facing toward the absorber layer 5 and the side 4b of the front contact layer 4 of the second solar cell 2.sub.m facing away from the absorber layer 5. Each second contact strip 7b contacts the side 3a of the rear contact layer 3 of the second solar cell 2.sub.m facing toward the absorber layer 5 and the side 4b of the front contact layer 4 of the third solar cell 2.sub.m.sub.+1 facing away from the absorber layer 5. In the region of the second solar cell .sub.2m, at least one first contact strip 7a and one second contact strip 7b extend in such a way that they overlap in the direction transverse to the series connection direction RS. This overlapping extension results in an interlocking structure of the first contact strips 7a on the one hand and the second contact strips 7b on the other hand on each solar cell 2, as can be seen in particular from FIGS. 1 to 3, 5, and 6. This enables the surface area of the solar cells 2 to be optimally included by the contact strips 7. As a result, electrical charges generated at any point in the absorber layer 5 of the solar cells 2 can travel on a relatively short path to the front contact layer 4 or rear contact layer 3 and from there to the contact strips 7.

[0061] In alternative embodiments, a first and a third solar cell do not adjoin a second solar cell on opposite sides, but instead, for example, on two adjacent sides of the second solar cell. In this case, the series connection directions for the electrical serial connection of the first and the second solar cell on the one hand and the second and third solar cell on the other hand differ. For example, these two series connection directions can then extend perpendicularly to one another or obliquely to one another at an acute angle.

[0062] In corresponding embodiments, as in the examples shown, the first contact strips 7a are arranged with equal transverse distance QA.sub.1 from one another in the region of a respective solar cell 2. In advantageous implementations, the transverse distance QA1 of the first contact strips 7a from one another is between 10 mm and 100 mm. In alternative embodiments, the first contact strips 7a can be arranged with different transverse distances.

[0063] In corresponding embodiments, as in the examples shown, the second contact strips 7b are arranged with equal transverse distance QA.sub.2 from one another. In advantageous implementations, the transverse distance QA.sub.2 of the second contact strips 7b from one another is between 10 mm and 100 mm. In alternative embodiments, they can be arranged with different transverse distances.

[0064] In corresponding embodiments, as in the examples shown, the first contact strips 7a and the second contact strips 7b are arranged alternating with equal transverse distance QA.sub.12 from one another. In advantageous implementations, the transverse distance QA.sub.12 of the first and second contact strips 7a, 7b from one another is between 5 mm and 50 mm. In alternative embodiments, they can be arranged with different transverse distances and/or in a non-alternating sequence in the transverse direction.

[0065] In advantageous embodiments, the contact strips 7 extend as in the example shown in the region of a respective solar cell 2 with a strip length KL, marked in FIG. 4, that is at least 50% of the longitudinal extension SL of the solar cell 2 in the extension direction of the contact strips 7, i.e., the cell width ZB. The strip length KL of the contact strips is preferably at least 80% of the linear extension SL of the solar cell 2. In the variant having continuous rear contact layer contacting in the respective connecting trench 9b, this also applies to the length of the connecting trench 9b or to the continuous contact surface of the contact strip 7 with the rear contact layer 3. It can also be provided that the contact strips 7 or the connecting trench 9b each end at a predefinable distance in the range of, for example, 1 mm to 15 mm from the adjacent solar cell or from the relevant separating strip region 12. In corresponding embodiments, the cell width ZB, i.e., the longitudinal extension SL of the respective solar cell 2 in the extension direction of the contact strips 7, is between 10 mm and 300 mm.

[0066] In advantageous implementations, the contact strips 7 extend in the region of a respective solar cell 2 at least with their strip section contacting the front contact layer 4 having a strip length KL that is less than the longitudinal extension SL of the solar cell 2 in the extension direction, i.e., the cell width ZB, by a shortening distance VA that is less, at most twice as large as a grid spacing GA of a contact grid structure 13, with which the front contact layer 4 is optionally provided in a manner conventional per se, as in the examples shown. In this case, the contact strips 7 can be attached over the contact grid structure 13 that has already been formed. Alternatively, the contact strips 7 can be attached first, before the contact grid structure 13 is then formed.

[0067] FIG. 17 shows the determined functional progression of the efficiency of the photoelectric conversion for the thin film solar module with varied cell breadth or cell width in diagram form for a typical, exemplary module design, wherein the cell width is abbreviated as cell width in FIG. 17. The determination of this progression or this characteristic curve can be verified both by computational simulation and by a corresponding series of experimental tests, wherein the efficiency is understood to mean the efficiency determined as usual under so-called STC conditions. It is obvious that the progression of the efficiency shown diagrammatically for a special module design according to the invention, indicated as usual in percent, was determined as a function of the cell width, indicated in centimeters, while keeping the other module parameters constant.

[0068] Apart from the characteristic series connection structure, this module design is based on typical module parameters. A molybdenum material was thus chosen for the rear contact layer 3, a zinc oxide material for the front contact layer 4, and a CIGS material for the absorber layer 5. The electrical sheet resistances were 0.6 Ω/sq for the molybdenum rear contact layer and 75 Ω/sq for the ZnO front contact layer. Furthermore, a contact finger structure having a finger width of 0.0073 cm and a finger spacing of 0.15 cm was used. A width and a thickness of the respective contact strip 7 of 0.03 cm each were selected for the characteristic contact strip structure, wherein the longitudinal extension of the contact strip 7 is adapted to the change of the cell width ZB in such a way that a distance of the respective contact strip 7 at each of its two ends from the adjacent separating region 12 remains constant, for example a uniform distance between the contact strip 7 and the adjacent separating region 12 of approximately 2 mm at both ends of the contact strip 7. The length/width ratio of the respective connecting trench 9b or the contact surface of the respective contact strip 7 to the rear contact layer 3 is in the case of a cell width between 0.5 cm and 30 cm in the range between approximately 15:1 and approximately 1,000:1. As can be seen from FIG. 17, a maximum W.sub.M of the efficiency of slightly more than 16.8% at a cell width ZB.sub.M of approximately 4 cm results for this module design. This result is remarkable insofar as the maximum efficiency of conventional module designs is at a significantly lower cell width, typically in the range of cell widths between 0.1 cm and 1.5 cm.

[0069] Another result that can be seen from FIG. 17 is the comparatively flat curve of the characteristic curve for the efficiency with varied cell width. On the one hand, at a cell width ZB of approximately 0.7 cm and on the other hand, especially at a relatively large cell width ZB of approximately 15 cm, an efficiency of approximately 16.5% still results in each case, which corresponds to a reduction in relation to the maximum efficiency W.sub.M of only approximately 0.3% in absolute terms and just under 2% in relative terms of the maximum value W.sub.M. This contrasts significantly with conventional module designs, which only work with series connection structures on the cell edge or with at most short contact strips. Although these module designs can have a similarly large efficiency maximum, as mentioned, usually at significantly smaller cell widths below 1.5 cm, there is a much stronger drop in efficiency, starting from this maximum, particularly in the direction of greater cell widths.

[0070] For example, for a module design used for comparison with conventional P1-P2-P3 structuring instead of the contact strip structure according to the invention, with otherwise identical module parameters, there is a comparably high maximum efficiency, but for a cell width ZB of approximately 0.6 cm, and the efficiency drops quickly with greater cell width ZB and only still reaches a value of approximately 10% at a cell width ZB of 4 cm. For another comparative example with short contact strips, which extend only slightly, for example over a maximum length of approximately 8 mm from the separating strip region to the respective solar cell, there is a maximum efficiency of approximately 16% for a cell width ZB of approximately 3 cm, for otherwise identical module parameters, with again a relatively steep drop in efficiency at greater cell width ZB to a value of less than 5% in absolute terms for a cell width ZB of 15 cm.

[0071] It is to be noted at this point that in the example under consideration in FIG. 17, even for a cell width of 30 cm, an efficiency of slightly more than 15% still results, which in absolute terms is therefore still only approximately 1.7% below the maximum value, i.e., only 10% below the maximum value in relative terms. This therefore clearly shows the advantages of the electrical connection structure according to the invention having the characteristic contact strips 7, when these extend over a significant part of the cell width ZB of the solar cells.

[0072] For the example in FIG. 17, a module design was selected in that variant in which the respective contact strip 7 continuously contacts the rear contact layer 3 of the relevant solar cell 2 along its extension and is introduced into the associated connecting trench 9b for this purpose. However, it has been shown that the variant with punctiform contacting of the rear contact layer 3 via the associated via openings 9a at equal length of the contact strips 7 has essentially the same properties with respect to efficiency as a function of the cell width ZB, i.e., a maximum efficiency at a relatively large cell width ZB of more than 2 cm and a relatively flat progression of the characteristic curve, in particular towards the side of increasing cell width ZB.

[0073] As the exemplary embodiments shown and those explained further above make clear, the invention provides a thin film solar module that can be produced with relatively little effort and makes it possible to achieve a high solar module efficiency, wherein the current transport losses can in particular also be kept comparatively low. The specific electrical connection structure using the special contact strips makes a significant contribution to this.

[0074] The front contact layer is contacted via the contact strips, optionally assisted by a conventional front contact grid structure. The rear contact layer is exposed from the front side, i.e., on its side facing toward the absorber layer, for which purpose the absorber layer is formed or removed in a correspondingly structured manner, and contacted by means of the contact strips. With an interlocking arrangement of the contact strips, the length of the current paths can be kept very short, which accordingly keeps the ohmic resistance losses low.

[0075] In this way, the invention enables or facilitates the production of relatively large-area solar cells with low area losses and low module voltages without undesired electrical losses due to long current paths within the front contact layer and the rear contact layer. By contacting the front contact layer and the rear contact layer over practically the entire longitudinal extension or at least over a large part of the longitudinal extension of the solar cells, electrical losses during current extraction and current injection are also minimized.