Layer structure for a solar roof or for a vehicle body component

Abstract

The present invention relates to a layer structure (14) comprising a first, transparent disk (22) and a second disk (28), as well as at least one solar cell (24) arranged between the disks (22, 28). According to the invention, an antireflective layer (18) is arranged on one side of the first disk (22) facing away from the solar cell (24), and optionally a hard coating (16) is arranged on one side of the antireflective layer (18) facing away from the first disk (22). Furthermore, an IR reflective layer (20) for infrared radiation is arranged on the side of the first disk (22) facing away from the solar cell.

Description

[0001] The present invention relates to a layer structure according to the preamble of claim 1.

[0002] The present invention further relates to a solar roof with such a layer structure according to claim 16 and to a vehicle roof with such a solar roof according to claim 17.

[0003] The present invention also relates to a vehicle roof with a displaceable cover according to claim 18, wherein the cover has a solar roof according to the invention.

[0004] The present invention further relates to a vehicle body component according to claim 19, which has a layer structure according to the invention.

[0005] Known layer structures for solar roofs of a vehicle have a first, transparent pane and a second pane, as well as a solar cell arranged between the panes.

[0006] Sunlight can fall through the first layer onto the solar cell, generating a photocurrent. To avoid reflection losses, conventional solar cells (amorphous solar cells (aSi), monocrystalline solar cells (cSi), or polycrystalline or multicrystalline solar cells (mSi)) are coated with a reflective layer that is tailored to the optical transition of light from the surrounding air into the solar cell. In conventional silicon-based solar cells, a silicon nitride (SiN) layer approximately 70 nm thick, which has the typical bluish color, is typically applied to the outer surface.

[0007] If a known solar cell is to be integrated into a layered structure that includes the first, outer transparent layer, such an anti-reflection layer is no longer optimal, since light now passes from the material of the first layer (with a different refractive index than air) into the solar cell. This results in high reflection losses, which significantly reduce the solar cell's efficiency.

[0008] Another disadvantage of conventional layered structures is the heating of the layered structure due to the incident sunlight. The solar cell only converts a portion of the light in the range of 350 to 1000 nm into photocurrent, and even then, only with an efficiency of typically 25%. An absorbed portion of the near-infrared component (NIR, greater than 1000 nm) is converted into heat. The resulting heating of the solar cell reduces the efficiency of the solar cell, which decreases by approximately 0.4% per degree of heating for cSi modules. Since panoramic roofs for vehicles, for example, can heat up considerably in the sun, this has a significant impact on energy yield, especially in summer.

[0009] It is therefore the object of the present invention to provide a layer structure in which these disadvantages are reduced.

[0010] This problem is solved by a layer structure according to the characterizing part of claim 1.

[0011] According to the invention, an anti-reflection layer is arranged on a side of the first pane facing away from the solar cell, and optionally a hard coating is arranged on a side of the anti-reflection layer facing away from the first pane. Furthermore, an IR reflection layer for infrared radiation is arranged on this side of the first pane facing away from the solar cell.

[0012] The side of the first pane facing away from the solar cell is the outer side of a layered structure installed on a vehicle. By applying an anti-reflective layer, reflection losses can be reduced because the anti-reflective layer can be optimized for the transition from the ambient air to the first pane or (when providing a hard coating) from the hard coating to the first pane. For this purpose, the refractive indices of the layers involved are taken into account in the usual way. The anti-reflective layer can be made of silicon nitride (SiN). The optional hard coating (for example made of SiOx or TiOx) offers the advantage that this anti-reflective layer is not exposed on the surface, but is protected against environmental influences and scratching by the adhesive coating.The hard coating itself can also be designed as an anti-reflective layer and thus perform both functions.

[0013] The provision of the IR reflection layer ensures that the incident infrared radiation, which on the one hand cannot be converted into a photocurrent by the solar cell and on the other hand heats the layer structure, is reflected back into the environment before reaching the first transparent pane.

[0014] Advantageous embodiments of the present invention emerge from the subclaims.

[0015] If the layer structure includes a hard coating, the IR-reflective layer can be positioned between the hard coating and the anti-reflective layer, or between the anti-reflective layer and the first pane. In both cases, the IR-reflective layer is also protected by the hard coating.

[0016] In an embodiment of the present invention in which no hard coating is provided, the IR reflection layer can be arranged between the anti-reflection layer and the first pane, or on the outside, i.e. the side of the anti-reflection layer that faces away from the first pane.

[0017] In particularly preferred embodiments of the present invention, both the IR reflection layer and the antireflection layer are optimized for the resulting transitions between the different optical paths (hard coating, IR reflection layer, antireflection layer, first transparent pane).

[0018] The IR-reflective layer is preferably optimized for the reflection of light with a wavelength greater than 1000 nm. When converting solar radiation into a photocurrent, only photons with a minimum energy corresponding to the band gap of the material can contribute to the photocurrent. For standard cSi cells, these are photons in the visible and near-IR spectrum between 400 and 1150 nm, with the greatest yield in the range between 600 nm and 900 nm (the visible range lies in the range from 400 nm to 780 nm). By providing an IR-reflective layer for the reflection of light with a wavelength greater than 1000 nm, the proportion of light that can only be used to a limited extent for the photocurrent but would heat the layer structure is reflected back into the environment.Preferably, the IR reflection layer is therefore optimized for the reflection of light in the near infrared range with wavelengths greater than 780 nm, in particular from 1000 nm to 3000 nm and / or the middle or far infrared range (wavelengths greater than 3000 nm).

[0019] In a further preferred embodiment of the present invention, for the reasons stated above, the anti-reflection layer is optimized for the transmission of light with a wavelength of less than 1000 nm, particularly visible light. This, in turn, is the portion of the sunlight spectrum that can be converted into photocurrent by the solar cell with high efficiency. This anti-reflection layer thus prevents a large portion of this "usable" light from being reflected back into the environment at the transitions of the optical media.

[0020] In principle, a thin-film solar cell, such as an amorphous thin-film solar cell, or a monocrystalline (cSi) or a polycrystalline thin-film solar cell (mSi) can be used as a solar cell.

[0021] An amorphous thin-film solar cell can be applied directly to the first transparent pane, for example by vapor deposition.

[0022] Alternatively, the solar cell can be applied to a separate substrate, which is then applied, for example laminated, to the first transparent pane.

[0023] The solar cell is advantageously designed as a thin-film solar cell and is partially transparent to visible light. This offers the advantage that, for example, when used in a vehicle roof, an at least partially transparent structure is formed through which a portion of the incident light is directed into the vehicle interior, thus creating a lighting situation similar to that of a glass roof without a solar cell.

[0024] In a particularly preferred embodiment of the present invention, a further IR reflection layer is provided, which can be designed in particular for the reflection of far-infrared radiation. This further IR reflection layer is arranged on a side of the second pane facing away from the solar cell, i.e., when used for a solar roof, on a side of the layered structure that is assigned to a vehicle interior. Such a "low-emissivity" (lowE) coating serves to reduce thermal radiation from the vehicle interior (when using the layered structure for a vehicle roof) into and through the layered structure. This offers the advantage, particularly at low temperatures, that the layered structure is endowed with a thermal insulation function.

[0025] In a further advantageous embodiment of the present invention, a thermoplastic and preferably transparent intermediate layer is arranged between the solar cell and the second pane. Such a thermoplastic intermediate layer, for example PVB (polyvinyl butyral), TPO (thermoplastic polyolefin), TPU (transparent polyurethane), EVAV, or EVA (ethylene-vinyl acetate copolymer), simplifies the assembly of the layer structure using a lamination process.

[0026] If the solar cell itself is not applied directly to the first transparent pane, but rather to a substrate, then such a thermoplastic intermediate layer is also advantageously arranged between the first pane and the solar cell, by means of which the substrate can be laminated together with the solar cell onto the first layer.

[0027] Advantageously, the first pane is formed as a glass pane, so that the layered structure has a scratch-resistant and stable structure. The second pane can also be designed as a transparent pane, preferably a glass pane. By using two glass panes, the layered structure is ideally suited for use in a vehicle's solar roof.

[0028] A solar roof according to the invention according to claim 16 therefore has a layer structure according to one of the preceding claims.

[0029] In a vehicle roof according to claim 17 with a solar roof according to claim 16, the solar roof is provided for firmly closing an opening in the vehicle roof, wherein here also the second pane is designed as a transparent pane, preferably as a glass pane, so that light can advantageously enter an interior of the vehicle.

[0030] In a vehicle roof according to claim 18, a cover for selectively opening and closing an opening in the vehicle roof includes a solar roof according to the invention according to claim 16 and here too the second pane is designed as a transparent pane, preferably as a glass pane.

[0031] However, a layer structure according to the invention can not only be used for a transparent or partially transparent solar roof, but can also form another vehicle body component, i.e. can be arranged at a completely different location on the vehicle body without providing for transparency of the vehicle body component.

[0032] In the following, the invention is explained in more detail using the attached figure as an example.

[0033] It shows: Fig. 1 a cross-section through a vehicle roof with a layer structure according to the invention.

[0034] Fig. 1 shows a cross-section through a vehicle roof 10 in the area of ​​a panoramic roof. A panoramic roof can represent fixed glazing for an opening in the vehicle roof. A layered structure 14 is provided in the vehicle roof 10, which is designed to be partially transparent, so that a portion of the incident light passes through the layered structure 14 as fully transmitted light 38. A further portion of the incident sunlight in the infrared range is reflected by the layered structure 14 as an IR portion 34. An IR reflection layer 20 is optimized for this purpose for reflecting light with a wavelength greater than 1000 nm.

[0035] Above the IR reflection layer 20, an anti-reflection layer 18 is arranged, which reduces the reflection of light with a wavelength of less than 1000 nm, in particular of visible light, and thus increases the transmission of light of this portion of the incident light spectrum.

[0036] The cross section through the layer structure 14 of the Fig. 1 is shown as the layer structure 14 is aligned in the installed state in the vehicle roof 10, so that sunlight is radiated from above onto the vehicle roof and partially transmitted through the layer structure 14 into a vehicle interior 40 below.

[0037] The IR-reflective layer 20 and the anti-reflective layer 18 can also be arranged in reverse. A hard coating 16 is also provided above these layers, in the illustrated embodiment above the anti-reflective layer 18. This hard coating 16 serves to protect the underlying layers from environmental influences and scratching.

[0038] Arranged beneath the anti-reflective layer 18 and the IR-reflective layer 20 is a first glass pane 22, which forms an outer pane or is assigned to an exterior space, and a second glass pane 28, which is assigned to the vehicle interior 40. A solar cell 24 is inserted between them, which is embedded between the two glass panes 22 and 28 by means of two thermoplastic intermediate layers 12 and 26. The solar cell 24 can be a cSi or mSi thin-film solar cell, i.e., a monocrystalline or polycrystalline thin-film silicon solar cell. The thermoplastic intermediate layers 12 and 26 can be made of a PVB, EVA, or TPU thermoplastic. The layer structure 14 is produced by means of a lamination process, wherein the thermoplastic intermediate layers 12 and 26 arranged on both sides of the solar cell 24 serve to embed the solar cell 24 in the layer structure 14 during the lamination process.On the underside of the layer structure 14, it further comprises a second IR reflection layer 30, which is designed as a "low" IR reflection layer. Like the first IR reflection layer 20, this layer also serves to reflect light in the infrared range, in this case, the reflection of a reflected IR component 36, which is emitted from the vehicle interior 40 toward the vehicle roof 10 and returned to the vehicle interior by means of the IR reflection layer 30.

[0039] The reflection of the IR portion of the sunlight radiated from outside (from above) into a reflected IR portion 34 reduces the heating of the layer structure 14 in this near-infrared (NIR) range above 1000 nm, since this portion cannot be converted into photocurrent by the solar cell 24 at all or only with very low efficiency. As already explained, the heating of the solar cell 24 would reduce its efficiency of typically 25% for converting visible light or light in a wavelength range from 350 to 1000 nm into electricity and significantly reduce the energy yield, especially in summer.

[0040] Conversely, the anti-reflection layer 18 for visible light ensures that a high proportion of the sunlight that can be converted into photocurrent by the solar cell 24 is radiated into the layer structure 14 and only a small proportion (not shown) is reflected back by the layer structure 14. This, in turn, increases the yield of photocurrent generated by the solar cell 24.

[0041] The low-E IR reflection layer 30, in turn, ensures that a large portion of the infrared radiation from the vehicle interior 40 is reflected back into the vehicle interior 40 as a reflected IR component 36. This also serves, on the one hand, to reduce the heating of the layer structure 14 in order to reduce the thermal losses of the solar cell 24. On the other hand, the IR reflection layer 30 also ensures the thermal insulation of the layer structure 14, which is particularly relevant in winter when a vehicle interior 40 heated by a vehicle heater should be prevented from experiencing excessive heat loss to the outside.

[0042] As already explained, in the Fig. 1 merely shows a schematic section through a layer structure 14 according to the invention of a vehicle roof 10. In addition to the layers shown, a black print can be provided (not shown here) in the form of a frit or an enamel, and this black print can extend along an edge region on one or both sides of the layer structure 14, i.e. not continuously over the entire layer structure 14. In this case, it can be provided that some of the layers which are in the Fig. 1, is removed in the area of ​​the black print before the black print is applied, so that the black print achieves optimal adhesion to one of the two glass panes 22 and 28. Preferably, the layers below the second glass pane 28 are removed, i.e., in the case shown, the IR-reflective layer 30, and only in the area where a black print is to be applied. For this purpose, the black print can have etching properties whose etching effect is adapted to the coating, and etches it away in areas where the black print is to adhere. The black print preferably extends from an outer edge of the first glass pane 22 or the second glass pane 28 to an outer edge of the solar cell 24.Such a black print can be used, for example, to cover electrical components or wiring required for the solar cell 24 so that they cannot be seen from the vehicle interior 40 or from an area outside the vehicle. Furthermore, layers for shading and / or displaying information can be provided, such as a PDLC, SPD, or LC.

[0043] Of course, the solar cell 24 is the Fig. 1 is only an exemplary representation and can also be replaced by a combination of several individual solar cells.

[0044] With the aid of the illustrated vehicle roof 10, the efficiency of the embedded solar cell 24 is significantly improved compared to known systems, since the heating of the layer structure 14 is reduced by the IR reflection layers 20 and 30. On the other hand, the proportion of partially transmitted light 32 that penetrates to the solar cell 24 and is at least partially converted into a photocurrent is increased by the anti-reflection layer 18, which further improves the efficiency of the solar cell 24. Because the entire layer structure 14 is partially transparent, including the solar cell 24, a proportion of incident sunlight, particularly in the visible range, penetrates the layer structure 14 to the vehicle interior 40, which improves the lighting situation in the vehicle interior 40.For this purpose, the solar cell 24 can be designed as a thin-film solar cell, and thus similar light transmission values ​​can be achieved as with conventional panoramic roofs without a solar cell, such as a transmission of visible light Tvis of typically 6% and a total transmitted solar energy TTS of typically 15%. List of reference symbols 10 Vehicle roof 12 first thermoplastic interlayer (PVB) 14 Layer structure 16 Hard coating 18 Anti-reflective coating 20 IR reflection layer 22 first glass pane 24 solar cells 26 second thermoplastic intermediate layer (PVB) 28 second glass pane 30 IR reflection layer (“lowE”) 32 partially transmitted light 34 reflected IR component 36 reflected IR component 38 fully transmitted light 40 Vehicle interior

Claims

[1] Layer structure (14) comprising a first transparent pane (22) and a second pane (28), as well as at least one solar cell (24) arranged between the panes (22, 28), characterized by , that an anti-reflection layer (18) is arranged on a side of the first pane (22) facing away from the solar cell (24), and optionally a hard coating (16) is arranged on a side of the anti-reflection layer (18) facing away from the first pane (22), and on the side of the first pane (22) facing away from the solar cell, an IR reflection layer (20) for infrared radiation is further arranged. [2] Layer structure (14) according to claim 1, characterized by that the layer structure (14) has the hard coating (16) and the IR reflection layer (20) is arranged between the hard coating (16) and the anti-reflection layer (18) or between the anti-reflection layer (18) and the first pane (22). [3] Layer structure (14) according to claim 1, characterized by that the IR reflection layer (20) is arranged between the anti-reflection layer (18) and the first pane (22), or is arranged on a side of the anti-reflection layer (18) which faces away from the first pane (22). [4] Layer structure (14) according to one of the preceding claims, characterized by that the IR reflection layer (20) is optimized for the reflection of light with a wavelength greater than 1000nm. [5] Layer structure (14) according to one of the preceding claims, characterized by that the IR reflection layer (20) is optimized for the reflection of light in the near-infrared range and / or far-infrared range. [6] Layer structure (14) according to one of the preceding claims, characterized by that the anti-reflection layer (18) is optimized for the transmission of light with a wavelength of less than 1000 nm, in particular for visible light. [7] Layer structure (14) according to one of the preceding claims, characterized by that the solar cell (24) is formed by a thin-film solar cell. [8] Layer structure (14) according to claim 7, characterized by that an amorphous thin-film solar cell is applied to the first transparent pane (22). [9] Layer structure (14) according to claim 7, characterized by that the thin-film solar cell is designed as a mono- or polycrystalline thin-film solar cell and is applied to a separate substrate. [10] Layer structure (14) according to one of claims 7 to 9, characterized by that the thin-film solar cell is partially transparent at least to visible light. [11] Layer structure (14) according to one of the preceding claims, characterized bythat on one side of the second pane (28) facing away from the solar cell (24), an IR reflection layer (30) for infrared radiation, in particular for far-infrared radiation, is arranged. [12] Layer structure (14) according to one of the preceding claims, characterized by that a second thermoplastic intermediate layer (26) is arranged between a substrate on which the solar cell (24) is arranged, or between the solar cell (24) and the second pane (28). [13] Layer structure (14) according to one of the preceding claims, characterized by that a first thermoplastic intermediate layer (12) is arranged between a substrate on which the solar cell (24) is arranged, or between the solar cell (24) and the first pane (22). [14] Layer structure (14) according to one of the preceding claims, characterized by that the first pane (22) is designed as a transparent pane, preferably as a glass pane. [15] Layer structure (14) according to one of the preceding claims, characterized by that the second pane (28) is designed as a transparent pane, preferably as a glass pane. [16] Solar roof (12) which has a layer structure (14) according to one of the preceding claims. [17] Vehicle roof (10) with a solar roof (12) according to claim 16 for firmly closing an opening in the vehicle roof (10), wherein the second pane (28) is designed as a transparent pane, preferably as a glass pane. [18] Vehicle roof (10) with a displaceable cover for selectively opening and closing an opening in the vehicle roof (10), wherein the cover includes a solar roof (12) according to claim 16, and the second pane (28) is designed as a transparent pane, preferably as a glass pane. [19] Vehicle body component which has a layer structure (14) according to one of the preceding claims 1 to 15 or a roof according to one of claims 16 to 18.

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