Solar module with homogeneous color impression

Abstract

A solar module with solar cells comprising a front covering with an outer and an inner surface and further comprising optically active zones with a first color, and optically inactive zones having a second color different from the first color. The front covering having a first dot grid covering the optically active zones, the first dot grid having a large number of opaque colored dots that have a third color different from the first color, wherein addition of the first color and the third color yields an additive color. The front covering having a second dot grid covering a optically inactive zone, the second dot grid having opaque colored dots having a fourth color different from the second color, wherein addition of the second color and the fourth color yields an additive color, wherein the third color and the fourth color are selected for a calculated color deviation.

Claims

1. A solar module with solar cells for photovoltaic energy generation, comprising: a front covering with an outer surface facing external surroundings and an inner surface facing the solar cells; optically active zones having a first color F.sub.1 with color coordinates L*.sub.1, a*.sub.1, b*.sub.1; and optically inactive zones having at least one second color F.sub.2, different from the first color F.sub.1, with color coordinates L*.sub.2, a*.sub.2, b*.sub.2; wherein the outer surface and/or the inner surface of the front covering comprise: at least one first dot grid that covers at least the optically active zones, wherein the at least one first dot grid has a large number of opaque colored dots having a third color F.sub.3, different from the first color F.sub.1, with color coordinates L*.sub.3, a*.sub.3, b*.sub.3, wherein addition of the first color F.sub.1 and the third color F.sub.3 yields an additive color F.sub.1′ with color coordinates L*.sub.1′, a*.sub.1′, b*.sub.1′, and at least one second dot grid that covers at least one of the optically inactive zones, wherein the at least one second dot grid has a plurality of opaque colored dots having a fourth color F.sub.4, different from the second color F.sub.2, with color coordinates L*.sub.4, a*.sub.4, b*.sub.4, wherein addition of the second color F.sub.2 and the fourth color F.sub.4 yields an additive color F.sub.2′ with color coordinates L*.sub.2′, a*.sub.2′, b*.sub.2′, and wherein the third color F.sub.3 and the fourth color F.sub.4 are selected such that a condition ΔE.sub.1,2≤5 is satisfied for color deviation
ΔE.sub.1,2=√{square root over ((L.sub.1.sup.*′−L.sub.2.sup.*′).sup.2+a.sub.1.sup.*′−a.sub.2.sup.*′).sup.2+(b.sub.1.sup.*′−b.sub.2.sup.*′).sup.2)}.

2. The solar module according to claim 1, wherein the third color F.sub.3 and the fourth color F.sub.4 are selected such that for the color deviation ΔE.sub.1,2 the condition ΔE.sub.1,2≤2, ΔE.sub.1,2≤1, or ΔE.sub.1,2≤0.5 is satisfied.

3. The solar module according to claim 1, wherein the opaque colored dots of the at least one first dot grid and/or of the at least one second dot grid have a size selected from the group consisting of less than 5 mm, less than 3 mm, and less than 1 mm.

4. The solar module according to claim 1, wherein the at least one first dot grid and/or the at least one second dot grid have a resolution of at least 80 dpi and the opaque colored dots of the first dot grid and/or second dot grid have a maximum dimension selected from less than 0.3 mm, less than 0.2 mm, and less than 0.1 mm.

5. The solar module according to claim 1, wherein the at least one first dot grid is configured such that a degree of coverage of the optically active zones is selected from less than 50%, less than 25%, less than 10%.

6. The solar module according to claim 1, wherein the at least one second dot grid is configured such that a degree of coverage of the at least one optically inactive zone or all optically inactive zones is selected from at least 95%, at least 97%, and at least 99%.

7. The solar module according to claim 1, wherein the at least one second dot grid is configured such that a degree of coverage of the at least one optically inactive zone or all optically inactive zones is 100%, wherein the additive color F.sub.2′ with the color coordinates L*.sub.2′, a*.sub.2′, b*.sub.2′ corresponds to the fourth color F.sub.4 with the color coordinates L*.sub.4, a*.sub.4, b*.sub.4.

8. The solar module according to claim 1, wherein the at least one second dot grid is configured such that a degree of coverage of the at least one optically inactive zone or all optically inactive zones is less than 95%.

9. The solar module according to claim 1, wherein the at least one first dot grid covers an inner region of the solar module.

10. The solar module according to claim 1, wherein the at least one second dot grid covers an optically inactive edge zone of the solar module.

11. The solar module according to claim 1, wherein optically inactive zones in the inner region are each covered by a second dot grid.

12. The Solar module according to claim 1, wherein the at least one first dot grid and the at least one second dot grid are arranged on the inner surface of the front covering.

13. The solar module according to claim 1, wherein the front covering is made of satinized glass with a haze value selected from greater than 50%, greater than 80%, and greater than 90%.

14. A method for producing a solar module for photovoltaic energy generation, comprising: providing a front covering with an outer surface facing external surroundings and an inner surface facing the solar cells; providing solar cells with optically active zones having a first color F.sub.1 with color coordinates L*.sub.1, a*.sub.1, b*.sub.1, and with optically inactive zones having at least one second color F.sub.2, different from the first color F.sub.1, with color coordinates L*.sub.2, a*.sub.2, b*.sub.2; applying on the outer surface and/or the inner surface of the front covering: at least one first dot grid that covers at least the optically active zones, wherein the at least one first dot grid has a large number of opaque colored dots having a third color F.sub.3, different from the first color F.sub.1, with color coordinates L*.sub.3, a*.sub.3, b*.sub.3, wherein addition of the first color F.sub.1 and of the third color F.sub.3 yields an additive color F.sub.3′ with color coordinates L*.sub.1′, a*.sub.1′, b*.sub.1′, and at least one second dot grid that covers at least one of the optically inactive zones, wherein the at least one second dot grid has a plurality of opaque colored dots having a fourth color F.sub.4, different from the second color F.sub.2, with color coordinates L*.sub.4, a*.sub.4, b*.sub.4, wherein addition of the second color F.sub.2 and the fourth color F.sub.4 yields an additive color F.sub.2′ with color coordinates L*.sub.2′, a*.sub.2′, b*.sub.2′; and selecting the third color F.sub.3 and the fourth color F.sub.4 such that a condition ΔE.sub.1,2≤5 is satisfied for color deviation
ΔE.sub.1,2=√{square root over ((L.sub.1.sup.*′−L.sub.2.sup.*′).sup.2+a.sub.1.sup.*′−a.sub.2.sup.*′).sup.2+(b.sub.1.sup.*′−b.sub.2.sup.*′).sup.2)}.

15. A building component comprising the solar module of claim 1.

16. The building component of claim 15, selected from the group consisting of a window, a façade, and a roof component.

Description

(1) The invention is now explained in detail using an exemplary embodiment, referring to the accompanying figures. They depict, in simplified, not to scale representation:

(2) FIG. 1 a schematic representation of the integrated serial connection of solar cells according to one embodiment of a solar module according to the invention implemented in the form of a thin-film solar module in a cross-sectional view;

(3) FIG. 2 a schematic representation of the light-entry-side surface of the thin-film solar module of FIG. 1 viewed from above;

(4) FIG. 3 a flowchart to illustrate the method according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) FIG. 1 schematically illustrates a thin-film solar module according to the present invention referenced as a whole with the number 1 using a cross-sectional view (section perpendicular to the module surface). The thin-film solar module 1 comprises a plurality of solar cells 16 serially connected to one another in integrated form, wherein, in a greatly simplified manner, only two solar cells 16 are depicted. Of course, generally speaking, in the thin-film solar module 1, a large number of solar cells 16 (for example, approx. 100 to 150) are serially connected.

(6) The thin-film solar module 1 has a composite pane structure in substrate configuration. It comprises a back substrate 2 with a layer structure 3 made of thin films applied thereon, wherein the layer structure 3 is arranged on a light-entry-side surface of the back substrate 2. The back substrate 2 is implemented here, for example, as a rigid flat glass plate with relatively high light permeability, wherein other electrically insulating materials with desired stability and inert behavior relative to the process steps performed can equally be used.

(7) The layer structure 3 includes, arranged on the light-entry-side surface of the back substrate 2, an opaque back electrode layer 5 that is made, for example, of a light-impermeable metal such as molybdenum (Mo) and was applied on the back substrate 2 by vapor deposition or magnetron enhanced cathodic sputtering (sputtering). The back electrode layer 5 has, for example, a layer thickness in the range from 300 nm to 600 nm.

(8) A photovoltaically active (opaque) absorber layer 6 made of a semiconductor doped with metal ions whose band gap is capable of absorbing the greatest possible share of sunlight is applied on the back electrode layer 5. The absorber layer 6 is made, for example, of a p-conductive chalcopyrite semiconductor, for example, a compound of the group Cu(In/Ga) (S/Se).sub.2, in particular sodium(Na)-doped Cu(In/Ga) (S/Se).sub.2. In the above formula, indium (In) and gallium (Ga) as well as sulfur (S) and selenium (Se) can be present alternatively or in combination. The absorber layer 6 has a layer thickness that is, for example, in the range from 1-5 μm and is, in particular, approx. 2 μm. For the production of the absorber layer 6, various material layers are typically applied, for example, by sputtering, which layers are subsequently thermally converted to form the compound semiconductor by heating in a furnace, optionally in an atmosphere containing S and/or Se (RTP=rapid thermal processing). 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.

(9) Deposited on the absorber layer 6 is a buffer layer 7, 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 in FIG. 1.

(10) A front electrode layer 8 is applied on the buffer layer 7, for example, by sputtering. The front electrode layer 8 is transparent to radiation in the visible spectral range (“window electrode”) such that the incoming sunlight 4 (symbolized in FIG. 1 by four parallel arrows) is weakened only slightly. The front electrode layer 8 is based, for example, on a doped metal oxide, for example, n-conductive aluminum (Al)-doped zinc oxide (ZnO). Such a front electrode layer 8 is generally referred to as a TCO layer (TCO=transparent conductive oxide). The layer thickness of the front electrode layer 8 is, for example, approx. 500 nm. By means of the front electrode layer 8, together with the buffer layer 7 and the absorber layer 6, a heterojunction (in other words, a succession of layers of the opposite conductor type) is formed. The buffer layer 7 can effect electronic adaptation between the absorber layer 6 and the front electrode layer 8.

(11) For protection against environmental influences, a (plastic) adhesive layer 9, which serves to encapsulate the layer structure 3, is applied on the front electrode layer 8. Glued with the adhesive layer 9 is a front or light-entry-side covering 10 transparent to sunlight, implemented, for example, in the form of a rigid (planar) glass plate made of extra white glass with low iron content. The front covering 10 is used for sealing and for mechanical protection of the layer structure 3. The front covering 10 has two opposite surfaces, namely, an inner surface 12 facing the solar cells 16 and an outer surface 11 facing away from the solar cells 16, which is, at the same time, the module surface. The thin-film solar module 1 can absorb sunlight 4 via the outer surface 11 in order to produce electrical voltage on the two voltage connections (+,−). A resulting current path is depicted in FIG. 1 by arrows arranged in series. The front covering 10 and the back substrate 2 are fixedly bonded to one another (“laminated”), with the adhesive layer 9 implemented here, for example, as a thermoplastic adhesive layer that is plastically deformable by heating and, upon cooling, fixedly bonds the covering 10 and the substrate 2 to one another. Here, the adhesive layer 9 is made, for example, of PVB. The covering 10 and the substrate 2 form a laminated composite together with the solar cells 16 embedded in the adhesive layer 9.

(12) For the implementation and serial connection of the solar cells 16, the layer structure 3 was patterned using a suitable patterning technology, for example, laser scribing and/or mechanical ablation. Typically, for this purpose, direct successions of, in each case, three patterning lines Pl-P2-P3 are introduced into the layer structure 3. Here, at least the back electrode layer 5 is subdivided by first patterning lines P1, producing the back electrodes 5-1, 5-2, of the solar cells 16. At least the absorber layer 6 is subdivided by second patterning lines P2, producing the absorbers 6-1, 6-2 of the solar cells 16. At least the front electrode layer 8 is subdivided by third patterning lines P3, producing the front electrodes 8-1, 8-2 of the solar cells 16.

(13) The front electrode 8-1 of one solar cell 16 is electrically connected to the back electrode 5-2 of an adjacent solar cell 16 via the second structuring line P2, with the front electrode 8-1, for example, directly contacting the back electrode 5-2. In the exemplary embodiment depicted, the trenches of the first patterning lines P1 are filled with material of the absorber layer 6. The trenches of the second patterning lines P2 are filled by material of the front electrode layer 8, and the trenches of the third patterning lines P3 are filled by the adhesive layer 9. Each direct succession of a first, second, and third patterning line Pl-P2-P3 forms a patterning zone 17. FIG. 1 depicts, by way of example, only one single patterning zone 17, by which the serial connection of two directly adjacent solar cells 16 is defined, with a large number of such patterning zones 17 provided for patterning and serially connecting solar cells 16 in the thin-film solar module 1.

(14) The optically active zones of the thin-film solar module 1 are identified in FIG. 1 by the reference number “14”. These are those regions of the solar cells 16 that have in each case, positioned atop one another in the form of a stack, a back electrode and an absorber as well as a front electrode and are capable of photoelectric conversion of sunlight 4 into electric current. For example, the optically active zone 14 of the solar cell 16 depicted on the left in FIG. 1 comprises the back electrode 5-1, the absorber 6-1, and the front electrode 7-1.

(15) The thin-film solar module 1 includes an inner region 18 that has the solar cells 16 and an edge region 13. The solar cells 16 in the inner region 18 comprise the optically active zones 14 and the optically inactive patterning zones 17. The optically inactive region 13 (completely) surrounds the inner region 18 peripherally. In the edge region 13, the layer structure 3 is removed. The edge region 13 serves, in particular, for the electrical contacting of the serially connected solar cells 16 by busbars (not shown). In FIG. 1, the optically inactive zones of the thin-film solar module (edge region 13, patterning zones 17) are identified by the reference number “15”.

(16) Reference is now made to FIG. 2 which schematically illustrates an exemplary embodiment of the light-entry-side surface of the thin-film solar module 1 of FIG. 1. According to it, a first dot grid 19 and a second dot grid 20 are applied on the inner surface 12 of the front covering 10. Viewed at a right angle through the front covering 10, i.e., relative to a direction perpendicular to the outer surface 11, the first dot grid 19 completely covers the inner region 18 of the thin-film solar module 1, i.e., the first dot grid 19 arranged only above or over the inner region 18. The shape and dimensions of the first dot grid 19 correspond to those of the inner region 18. Viewed at a right angle through the front covering 10, i.e., relative to the direction perpendicular to the outer surface 11, the second dot grid 20 completely covers the edge region 13 of the thin-film solar module 1, with the second dot grid 20 arranged only over the edge region 13. The shape and dimensions of the second dot grid 19 correspond to those of the edge region 13. As indicated in FIG. 2, the first dot grid 19 and the second dot grid 20 are discernible in each case from the external surroundings through the front transparent covering 10.

(17) The first dot grid 19 is composed of a large number of opaque colored dots 21 that are arranged in the form of a checkerboard pattern with equal distances therebetween. Situated between the opaque colored dots 21 are transparent locations 22 of the front covering 10 such that the optically active zones 14 are discernible through the front covering 10. The first dot grid 19 has a resolution of at least 80 dpi, with the individual colored dots 21 having in each case a maximum dimension of less than 0.3 mm. The degree of coverage of the optically active zones 14 by the colored dots 21 of the first dot grid 19 is 50% (area share of the colored dots 21), in other words, with a perpendicular view through the front covering 10 or (perpendicular) projection of the optically active zones 14 on the inner surface 11, the opaque colored dots 21 of the first dot grid 19 occupy 50% of the area of the optically active zones 14. Situated in the remaining region of the optically active zones 14 are transparent locations 22. Correspondingly, the optical (semi-)transparency of the front covering 10 in the inner region 18 is 50%. As a result, the loss of efficiency due to reduction of the optical transparency of the front covering 10 can be minimized.

(18) The second dot grid 20 is analogously composed of a large number of opaque colored dots 21, with the degree of coverage of the optically inactive edge region 13 at least 95%, in other words, with a perpendicular view through the front covering 10 or (perpendicular) projection of the edge region 13 the inner surface 11, the colored dots 21 of the second dot grid 20 occupy at least 95% of the area of the edge region 13. The colored dots 21 have a correspondingly small distance between them such that they are no longer discernible as individual colored dots 21 in FIG. 2. Instead, the second dot grid 20 substantially corresponds to a full-surface color coating. Consequently, the edge region 13 is virtually no longer discernible through the front covering 10, with the optical transparency of the front covering 10 in the edge region 13 amounting to a maximum of 5% (in other words, opaque covering 10 in the edge region 13).

(19) In FIG. 1, the two dot grids 19, 20 are schematically depicted (with greatly enlarged layer thickness of the print for better identification).

(20) In FIG. 2, the various colors of the thin-film solar module are depicted by way of example using gray tones. The optically active zones 14 have (due to production conditions) a first color F.sub.1 that is defined by the color coordinates L*.sub.1, a*.sub.1, b*.sub.1. The opaque colored dots 21 of the first dot grid 19 have a third color F.sub.3 different from the first color F.sub.1 and having the color coordinates L*.sub.3, a*.sub.3, b*.sub.3. Since the first color F.sub.1 is visible through the transparent locations 22, the first color F.sub.1 and the third color F.sub.3 are added in the inner region 18 of the thin-film solar module 1 to yield an additive color F.sub.1′ with the color coordinates L*.sub.1′, a*.sub.1′, b*.sub.1′. Viewed on the front covering 10, in other words, for a viewer observing the thin-film solar module 1 from the external surroundings, there is, thus, a color impression in the inner region 18 that corresponds to an addition (additive color mixing) of the two colors F.sub.1 and F.sub.3 to form the additive color F.sub.1′. Thus, there is, for the viewer, an averaged color impression from the background color of the optically active zones 14 and the color of the opaque colored dots 21 of the first dot grid 19. The additive color F.sub.1′ can be determined in a simple manner by a conventional colorimeter (spectral photometer), which is placed for this purpose, for example, with a measuring aperture on the outer surface of the front covering 10. Also possible would be a measurement of the additive color F.sub.1′ at a distance of, for example, 1 to 2 m from the outer surface 11. It is essential here that for an addition of the two colors F.sub.1 and F.sub.3 to form the additive color F.sub.1′, a region of the outer surface 11 of the front covering 10 with a size of at least 0.2 cm.sup.2 is considered.

(21) In the edge region 13, the thin-film solar module 1 has (due to production conditions) a second color F.sub.2 different from the first color F.sub.1 and defined by the color coordinates L*.sub.2, a*.sub.2, b*.sub.2. In FIG. 2, the second color F.sub.2 is no longer discernible through the second dot grid 20 applied substantially over the entire surface. The opaque colored dots 21 of the second dot grid 20 have a fourth color F.sub.4, different from the second color F.sub.2 and defined by the color coordinates L*.sub.4, a*.sub.4, b*.sub.4. In the edge region 13, the second color F.sub.2 and the fourth color F.sub.4 are thus added to yield an additive color F.sub.2′, defined by the color coordinates L*.sub.4′, a*.sub.4′, b*.sub.4′. As a result of the very low optical transparency in the edge region 13, the additive color F.sub.2′ corresponds substantially to the fourth color F.sub.4 of the opaque colored dots 21 of the second dot grid 20. Accordingly, there is, viewed on the front covering 10, i.e., for a viewer observing the thin-film solar module 1 from the external surroundings, a color impression in the edge region 13 that corresponds to the additive color F.sub.2′, i.e., substantially to the fourth color F.sub.4 of the opaque colored dots 21.

(22) In the production of the two dot grids 19, 20, the third color F.sub.3 and the fourth color F.sub.4 are selected such that for the color distance resulting from the formula
ΔE.sub.1,2=√{square root over ((L*.sub.1′−L*.sub.2′).sup.2+(a*.sub.1′−a*.sub.2′).sup.2+(b*.sub.1′−b*.sub.1′).sup.2)}

(23) the condition ΔE.sub.1,2≤5 is satisfied.

(24) In practice, in the selection of the colors, the fourth color F.sub.4 of the second dot grid 20 can be selected such that there is the least possible contrast with the third color F.sub.3 of the colored dots 21 of the first dot grid 19. Typically, the fourth color F.sub.4 of the second dot grid 20 is darker than the third color F.sub.3. As a practical manner, starting with a suitably covering fourth color F.sub.4 of the second dot grid 20, the lightest possible third color F.sub.3 is then selected. In the case of cell areas with residual coloration, their color should be taken into account during the color mixing. If the resolution of the opaque colored dots 21 is relatively small, then the contrast between the third color F.sub.3 of the opaque colored dots 21 of the first dot grid 19 and of the first color F.sub.1, in other words, the background color, of the cell areas (i.e., optically active zones 14) should not be too great, as a result of which, however, the required degree of coverage and, thus, the loss of efficiency can increase. In the case of higher resolution, homogeneous color adaptation, even with strong contrasts between opaque colored dots and darker cell areas can be achieved.

(25) In the exemplary embodiment of FIG. 2 the ratio of the L* values of the light dots of the first dot grid 19 to the L* values of the dots of the second dot grid 20 in the edge region 13 at 50% coverage to black is approx. 1.4:1. Thus, a sharp contrast between the colors in the edge region 13 and the inner region 18 can be avoided. The overall color impression (for example, from a distance of 1 m) from opaque colored dots 21 and transparent locations 22 in the inner region 18 is as close as possible to the color impression of the optically inactive zone 15 in the edge region 13; in other words, the additive color mixing of the opaque colored dots 21 (color F.sub.3) and the residual reflection of the cell areas (color F.sub.1) yield a color F.sub.1′, whose brightness, tone, and saturation deviate in each case less than 5% relatively (preferably 2%, better yet 1%) from the brightness, tone, and saturation of the fourth color F.sub.4 (corresponds substantially to the second additive color F.sub.2′) over the optically inactive zone 15 in the edge region 13.

(26) For the selection of the right colors, the person skilled in the art has access to various techniques and methods that are not the subject matter of this invention. For two cases, this is to be illustrated at this point only by way of example and in a simplified manner. The RGB color space is to be used here for the calculation of the colors. Tables or programs are available for the conversion of CIE-L*a*b* into RGB.

(27) Case 1: The active cell area is virtually black (F.sub.1 in RGB=(0,0,0)) as can nearly be achieved with thin-film solar modules based on Cu(In,Ga) (S,Se).sub.2 under suitable processing conditions. The desired color of the module F.sub.1′ is gray, for example, RGB (64,64,64). For the least possible coverage with the first dot grid, white (256, 256, 256) must thus be used as color F.sub.3. The degree of coverage of the first dot grid is thus calculated at 25%. Then, for the edge covering, with 100% coverage of the second dot grid, the color F.sub.4=F.sub.2′=F.sub.1′=(64,64,64) can be selected.

(28) Case 2: A customer wants a blue module with the RGB color code (0,50,114). The active area is black (RGB 0,0,0). The edge covering should, because of the metallic contact bands, be as opaque as possible; thus, a degree of coverage of 100% is desired for the second dot grid. In order to achieve the least possible coverage in the active cell area, the color F.sub.3 of the dots of the first grid must have the brightest possible tone. However, the brightness and saturation of the color must not change. Limiting is the brightest color coordinate, here in RGB, consequently, blue (114). The maximum blue value is 256 in the RGB color space. The maximum coverage is thus 114/256=44%. For the RGB color code of the color F.sub.3 of the individual points, F.sub.3=(0, 113, 256) is then obtained.

(29) Although this is not depicted in the exemplary embodiment of FIG. 2, it would be equally possible to provide a second dot grid 20 in each case (completely) covering the patterning zone 17. This can improve the color homogeneity of the thin-film solar module 1 even further.

(30) Reference is now made to FIG. 3, in which an exemplary embodiment of the method according to the invention is illustrated. The method comprises a first step I, wherein a front covering 10 with an outer surface 11 facing the external surroundings and an inner surface 12 facing the solar cells 16 is provided. In a second step II, at least one first dot grid 19 that covers at least the optically active zones 14 of the solar cells 16 is applied on the inner surface 12 and/or the outer surface 11 of the front covering 10. The first dot grid 19 has a large number of opaque colored dots 21, which have a third color F.sub.3 different from the first color F.sub.1 of the optically active zones 14 and having the color coordinates L*.sub.3, a*.sub.3, b*.sub.3, wherein addition of the first color F.sub.1 and the third color F.sub.3 yields an additive color F.sub.1′ having the color coordinates L*.sub.1′, a*.sub.1′, b*.sub.1′. In a third step III, at least one second dot grid 20 that covers the optically inactive zones 15 is applied on the inner surface 12 and/or the outer surface 11 of the light-entry-side covering 10. The second dot grid 2 has a large number of opaque colored dots 21 that have a fourth color F.sub.4 different from the second color F.sub.2 and having the color coordinates L*.sub.4, a*.sub.4, b*.sub.4, wherein addition of the second color F.sub.2 and the fourth color F.sub.4 yields an additive color F.sub.2′ having the color coordinates L*.sub.2′, a*.sub.2′, b*.sub.2′. The third color F.sub.3 and the fourth color F.sub.4 are selected such that for the color distance
ΔE.sub.1,2=√{square root over ((L*.sub.1′−L*.sub.2′).sup.2+(a*.sub.1′−a*.sub.2′).sup.2+(b*.sub.1′−b*.sub.1′).sup.2)}

(31) the condition ΔE.sub.1,2≤5 is satisfied.

(32) The first dot grid 19 and the second dot grid 20 are applied on the front covering 10 using, for example, the screenprinting or digital printing method.

(33) The invention makes available an improved solar module as well as a method for production thereof, which avoids a sharp contrast between optically active and optically inactive zones. Advantageously, the solar module gives a very homogeneous color impression over the complete module with little or no directional dependency of the color impression. The relatively low rate of coverage of the at least one dot grid in the inner region of the solar module enables minimizing the efficiency loss of the solar module.

LIST OF REFERENCE CHARACTERS

(34) 1 thin-film solar module

(35) 2 back substrate

(36) 3 layer structure

(37) 4 sunlight

(38) 5 back electrode layer

(39) 5-1, 5-2 back electrode

(40) 6 absorber layer

(41) 6-1, 6-2 absorber

(42) 7 buffer layer

(43) 8 front electrode layer

(44) 8-1, 8-2 front electrode

(45) 9 adhesive layer

(46) 10 front covering

(47) 11 outer surface

(48) 12 inner surface

(49) 13 edge region

(50) 14 optically active zone

(51) 15 optically inactive zone

(52) 16 solar cell

(53) 17 patterning zone

(54) 18 inner region

(55) 19 first dot grid

(56) 20 second dot grid

(57) 21 colored dot

(58) 22 transparent location