PHOTOVOLTAIC ELEMENT WITH OPTICALLY FUNCTIONAL CONVERSION LAYER FOR IMPROVING THE CONVERSION OF THE INCIDENT LIGHT AND METHOD FOR PRODUCING SAID PHOTOVOLTAIC ELEMENT

Abstract

The invention relates to a photovoltaic element including an optically functional surface layer for improving a conversion of the incident light. The functioning of the layer involves absorbing incident sunlight having a low wavelength and emitting it again as light radiation having a higher wavelength, so that this light spectrum becomes usable for solar cells. In order to solve the currently unsolved problem of embedding such a layer into a thin-film solar cell with a substrate arranged on the front side, while ensuring high weathering resistance, it is proposed to arrange the optical functional layer in an additional encapsulation element on the front side and thus to construct the photovoltaic element as a double- or multiple composite assembly.

Claims

1.-9. (canceled)

10. The method according to claim 13, wherein a foil is used as the intermediary layer.

11. The method according to claim 13, wherein the intermediary layer is applied to the glass- or plastic material plate or -foil as a lacquer, gel, emulsion, glue or paste before the glass- or plastic material plate or -foil is arranged on the substrate.

12. (canceled)

13. A method for producing a photovoltaic element for converting light into electrical power, the method comprising the steps: producing a thin film solar cell including a transparent substrate that is arranged directly on a front side of the thin film solar cell which front side is adapted to receive incident light; arranging an encapsulation element on the transparent substrate after producing the thin film solar cell, wherein the encapsulation element includes a transparent glass- or plastic material plate or -foil, wherein the encapsulation element includes a conversion layer with an optically functional material which absorbs light of a particular wavelength range and reemits the light as a light of a different wavelength range which provides the incident light received by the thin film solar cell, wherein the encapsulation element is arranged on the transparent substrate of the thin film solar cell for protecting the thin film solar cell against environmental impacts, wherein an interconnection forming intermediary layer is arranged between the transparent substrate and the glass- or plastic material plate or -foil, and wherein the optically functional material is arranged in the intermediary layer or in the glass- or plastic plate or -foil.

14. The method according to claim 13, wherein the intermediary layer is provided as the conversion layer, and wherein the conversion layer is arranged between the substrate of the thin film solar cell and the glass- or plastic material plate or -foil.

15. The method according to claim 13, wherein the conversion layer is arranged between the substrate of the thin film solar cell and the glass- or plastic material plate or -foil, or wherein the conversion layer is provided as the glass- or plastic material plate or -foil, and wherein the optically functional material is arranged in the glass- or plastic material layer or -foil,

16. The method according to claim 13, wherein the conversion layer is provided as an emulsion, a gel, a paste, a lacquer, a glue or a foil.

17. The method according to claim 13, wherein the photovoltaic element includes a plurality of thin him solar cells which are configured and arranged in a superstrate configuration as monolithically electrically connected thin film packets in a uniform manner on the substrate.

18. The method according to claim 13, wherein the encapsulation element is provided so that it has at least one of the following properties: reflection reduction, scratch resistance and self-cleaning.

19. The method according to claim 13, wherein the photovoltaic element includes the encapsulation element directly on the front side on the substrate, wherein the encapsulation element includes the following layers: a first interconnection forming intermediary layer which is directly arranged on the substrate, and a first transparent glass- or plastic material plate or -foil arranged on the first interconnection forming intermediary layer.

20. The method according to claim 13, wherein the photovoltaic element includes a second encapsulation element directly on a backside on the thin film solar cell, wherein the second encapsulation element includes the following layers; a second interconnection forming intermediary layer which is arranged on the thin film solar cell, and a second transparent glass- or plastic material plate or -foil arranged on the second interconnection forming intermediary layer.

21. A method for producing a photovoltaic element for converting light into electrical power, the method comprising the steps: producing a thin film solar cell including a transparent substrate that is arranged directly on a front side of the thin film solar cell which front side is adapted to receive incident light: arranging an encapsulation element on the transparent substrate after producing the thin film solar cell, wherein the encapsulation element includes a transparent glass- or plastic material plate or -foil, wherein the encapsulation element includes a conversion layer with an optically functional material which absorbs light of a particular wavelength range and reemits the light as a light of a different wavelength range which provides the incident light received by the thin film solar cell, wherein the encapsulation element is provided as an interconnection of a plurality of layers, wherein the encapsulation element includes an interconnection forming intermediary layer which establishes an interconnection between the encapsulation element and the transparent substrate of the thin film solar cell, wherein the optically functional material is arranged in the intermediary layer and in the glass- or plastic material plate or -foil.

22. The method according to claim 13, wherein the intermediary layer id formed by an EVA foil, a PVB foil or a PE foil.

23. The method according to claim 13, further comprising the step: applying the intermediary layer as a lacquer, a gel, an emulsion, a glue or a paste before arranging the glass plate or the foil on the transparent substrate.

24. The method according to claim 13, wherein the encapsulation element is provided as an interconnection of a plurality of layers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Certainly a foil and also a glue or similar can be provided as well as two intermediary layers. Preferably, however, only one intermediary layer is used. Further advantages and features of the invention are described with reference to embodiments based on the drawing figures, wherein:

[0028] FIG. 1 illustrates a schematic not to scale cross-section through the structure of a thin film solar module; and

[0029] FIG. 2 illustrates a diagram including:

[0030] an intensity of incident sunlight in various wavelength ranges,

[0031] an absorption spectrum of a solar cell illustrated with reference to an

[0032] embodiment of a cadmium-telluride solar cell, and

[0033] possible absorption- and emission ranges of the conversion layer.

DETAILED DESCRIPTION OF THE INVENTION

[0034] FIG. 1 illustrates a schematic cross-section of a thin film solar module 1 which includes a thin film solar cell 2 with a thin film packet 3 and a substrate 4. On the front side of the thin film cell 2, a conversion layer 5 and thereon a first protective layer is arranged which is configured for example as first glass- or plastic plate or foil 6. The conversion layer 5 is thus configured as first interconnection generating intermediary layer, namely for example as a transparent glue foil, in particular EVA, PVB or PE foil in which the optically functional material is embedded. On the backside of the thin film solar cell 2, a second interconnection forming intermediary layer 7 is arranged that is typically also configured as transparent glue foil or a second protection layer which is configured as second glass or plastic plate or foil 8, wherein the layer thicknesses are not illustrated to scale. Above the layer structure, the incident solar radiation is schematically illustrated through parallel arrows.

[0035] The second glass- or plastic plate or -foil 8 of the solar module typically has a thickness of 2 mm to 3 mm. Also the substrate 4 and the first glass- or plastic plate or -foil 6 have a thickness of approximately 2 mm to 3 mm. This particular configuration yields a three-pane interconnection which has particularly high stability. Alternatively as described supra, also particular thicknesses can be reduced while maintaining the typical overall stability.

[0036] The thin film packet 3 of the thin film solar cell 2 includes a positively doted semiconductor layer and a negatively doted semiconductor layer and electrical contacts on the front side and on the backside, wherein the electrical contact on the side oriented towards the light is made from transparent metal oxides, the negative semiconductor layer is made from cadmium sulfite and the positive semiconductor layer is made from cadmium telluride and the electrical contact on the backside is made from a metal material. Thus, overall, the entire thin film packet 3 is only a couple of micrometers thick, so that it is combined into one layer in the figure.

[0037] Thus, it is evident that the photovoltaic element 1 according to the invention does not only include a backside encapsulation element 9 which is formed from the second interconnection forming intermediary layer 7 and the second glass- or plastic plate or -foil 8, but also a front side encapsulation element 10 which is formed from the first interconnection forming intermediary layer 7 and the first glass- or plastic plate or -foil 8. This front side encapsulation element 10 is configured in the illustrated embodiment as an interconnection of plural layers 5, 6. The first intermediary layer 5 includes optically functional particles which are embedded in a suitable carrier medium; presently the particles are included in the foil. Thus, the carrier medium is also used as weather protection for the optically functional particles. Additional weather protection for the conversion layer 5 is provided through the first glass- or plastic plate or -foil 6.

[0038] Alternatively or additionally, it can also be provided that the first glass- or plastic material plate or -foil includes the optically functional material.

[0039] The production method according to the invention is particularly simple and cost-effective because the first glass- or plastic plate or -foil 6 is simply connected with the substrate 4 for this purpose. Thus, either an interconnection forming intermediary layer in the form of a glue is arranged in between or the entire packet is laminated, preferably simultaneously with a lamination of the frontal encapsulation element 9. Alternatively or additionally also the first glass- or plastic material plate or foil 6 can be provided with a paste, a lacquer or similar and is subsequently arranged on the substrate 4 and laminated.

[0040] Eventually also a single layer configuration of the frontal encapsulation element 10 can be provided where no interconnection forming intermediary layer 5 is provided, but the substrate 4 and the glass- or plastic material plate or -foil 6 are directly connected with one another. Then the conversion layer would form a unit with the first glass- or plastic material plate or -foil, wherein optically functional material is accordingly received in the first glass- or plastic plate or -foil.

[0041] FIG. 2 illustrates the utility that can be derived from the LDS method for a solar cell. Thus, the wavelength range of the incident sunlight (solid line) and also the absorption range of a solar cell based on cadmium telluride (dotted line) are drawn in a diagram. The wavelength of the incident light is thus plotted over the x-axis. A y-axis is drawn at the left and also at the right edge of the diagram, wherein the left y-axis indicates a relative intensity of the sunlight with a maximum of 1, the right y-axis on the other hand side indicates the relative absorption of the solar cell, also with the maximum of 1. Thus, however it is appreciated that the axes designate the same relative intensities but different absolute intensities. Thus, there is no wavelength range in which the solar cell can absorb more light than emitted by the sun.

[0042] It is apparent that the radiation of the sunlight spectrum starts at wavelengths of slightly above 200 nm. Then there is a sharp increase up to a maximum at approximately 500 nm, subsequently the intensity is continuously reduced. At a wavelength of 1000 nm, the wavelength has decreased to approximately 50% of its maximum. Radiation with longer wavelengths is not relevant for the invention and therefore not drawn.

[0043] The cadmium telluride solar cell, however, is capable of using light starting at a wavelength of approximately 450 nm for energy production. Thereafter, there is a quick increase of the absorption capability up to a maximum of 500 nm, thereafter the absorption capability decreases continuously. At slightly above 900 nm, there is an instant drop. Light with higher wavelengths cannot be used in practical applications.

[0044] Additionally, the diagram illustrated in FIG. 2 includes flat blocks which illustrate the possible absorption range (hatched block) and also the possible emission range (checkered block) of a conversion layer including optically functional material for light wave downshifting. Thus, these blocks do not represent the entire spectrum of the conversion layer but only represent possible ranges.

[0045] Thus it is apparent that the absorption spectrum is in a range of approximately 350 to 475 nm, thus in the high energy wavelength range of the sunlight which, however, cannot be absorbed by the solar cell. The emission spectrum in turn is in a range of 600 to 800 nm and therefore in the range of a high absorption of the solar cell.

REFERENCE NUMERALS AND DESIGNATIONS

[0046] 1 photovoltaic element

[0047] 2 thin film solar cell

[0048] 3 thin film packet

[0049] 4 substrate

[0050] 5 first interconnection forming intermediary layer/conversion layer

[0051] 6 first glass- or plastic material plate or -foil

[0052] 7 second interconnection forming intermediary layer

[0053] 8 second glass- or plastic material plate or -foil

[0054] 9 rear encapsulation element

[0055] 10 front encapsulation element