Abstract
A structure, in particular for use in thin layer cells, includes a reflector and an absorbing layer, wherein the reflector has an upper side and a lower side, wherein the upper side is oriented towards the absorbing layer, and wherein at the upper side the reflector comprises a cavity consisting of dielectric material.
Claims
1.-14. (canceled)
15. A structure for use in thin layer cells, comprising: a reflector; and an absorbing layer; wherein the reflector has an upper side and a lower side; wherein the upper side is oriented towards the absorbing layer; wherein at the upper side the reflector comprises a cavity consisting of dielectric material; wherein the absorbing layer has a planar top surface and a planar bottom surface; and wherein the bottom surface is in close proximity to the upper side of the reflector.
16. The structure according to claim 15, wherein the absorbing layer directly contacts ate least one of the material of the reflector and the cavity.
17. The structure according to claim 15, wherein the absorbing layer has a thickness of 5 nm to 10 microns.
18. The structure according to claim 17, wherein the absorbing layer has a thickness of 50 nm to 5 microns.
19. The structure according to claim 18, wherein the absorbing layer has a thickness of 200 nm to 5 microns.
20. The structure according to claim 15, wherein the absorbing layer consists of at least one of Crystalline Silicon (Si or C-Si),Amorphous Silicon (a-Si), Copper Indium Gallium Selenide Cu(In,Ga)Se2 (CIGSe), Indium Gallium Selenide (InGaAs) and, Organic absorbers.
21. The structure according to claim 15, wherein the reflector consists of a reflector base and a cavity cladding, wherein the cavity cladding abuts the cavity, and wherein the cavity cladding is adhesively bonded to the reflector base.
22. The structure according to claim 15, wherein the cavity has a symmetrical shape to enhance the absorbing of radiation with different polarization states.
23. The structure according to claim 15, wherein the cavity has a rectangular shape to enhance the absorbing of radiation especially for one polarization state.
24. The structure according to claim 15, wherein the reflector material is at least one of silver, aluminum and molybdenum.
25. The structure according to claim 20, wherein the cavity has a cavity width and the cavity cladding has a cladding width, and wherein the ratio between the cavity width of the cavity and the cladding width of the cavity cladding is about 0.4 to 1.8.
26. The structure according to claim 25, wherein the ratio between the cavity width of the cavity and the cladding width of the cavity cladding is 0.6 to 1.6.
27. The structure according to claims 15, wherein the cavity has a cavity height and the reflector base has a base height, and wherein the cavity height is between 5 nm and 5 microns.
28. The structure according to claim 27, wherein the cavity height is between 10 nm and 2 microns.
29. A cell structure comprising: an absorbing layer; and a reflector; wherein the reflector has an upper side; wherein the upper side is oriented towards the absorbing layer; and wherein at the upper side the reflector comprises a pattern of cavities; wherein each cavity consists of dielectric material; wherein the absorbing layer has a planar top surface and a planar bottom surface; and wherein the bottom surface is in close proximity to the upper side of the reflector.
30. The cell structure according to claim 29, wherein the cavities are separated by cavity claddings consisting of metal, and wherein the cavity claddings are part of the reflector.
31. The cell structure according to claim 29, wherein the cell structure includes the features of a structure according to claim 15.
32. A process for generating a tuned structure, for use in thin layers, comprising: defining an optimized geometry of a structure via a computer-based tuning step, wherein the tuning step optimizes at least the geometry of a cavity formed in a reflector.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 shows a first schematic view of a preferred embodiment of the current invention;
[0030] FIG. 2 shows a perspective, explosion view of the elements in a preferred embodiment of the current invention;
[0031] FIG. 3 shows a schematic view of a preferred embodiment of the cell structure according to the current invention;
[0032] FIG. 4 shows a diagram with test results conducted by the applicant with a cell structure according to the current invention; and
[0033] FIGS. 5a-5d show four schematic perspective views of different embodiments of the absorbing structure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] FIG. 1 clarifies the arrangement of the elements of an absorbing structure 1 according to a preferred embodiment of the current invention. The absorbing structure 1 comprises an absorbing layer 4 and a reflector 2 wherein the reflector has an upper side 22 and a lower side 24. At its upper side 22 the reflector 2 contacts a bottom surface 44 of the absorbing layer 4. The top surface 42 and the bottom surface 44 of the absorbing layer 4 are planar, which in other words means that there are no deliberately introduced irregularities in thickness. At the upper side 22 of the reflector 2 there is arranged a cavity 6 abutting the absorbing layer 4. The cavity 6 is filled with dielectric material, preferably glass. Certain shapes and geometry information of the cavity 6 is shown only very schematically in FIG. 1. These details can be found at the preferred embodiments shown in FIG. 2 and FIGS. 5a-5d.
[0035] FIG. 2 shows an explosion view of the preferred elements of an absorbing structure 1. In this preferred embodiment the reflector 2 is divided into a reflector base 25 and two cavity claddings 26 while for means of better perception of the different elements the cavity claddings 26 are shown separated from the reflector base 25. In a final state of the absorbing structure 1 it is to be understood that the cavity claddings 26 are bound or fixed to the reflector base. In another preferred embodiment of the invention the cavity cladding 26 or the plurality of cavity claddings is forming one part together with the reflector base 25. Furthermore preferred, the cavity 6 has a basically cubic shape. The cavity claddings 26 have a cladding width W.sub.cl, while the cladding width W.sub.cl is the sum of the width of two cavity claddings 26 neighbouring one cavity 6. The cavity 6 has a cavity width W.sub.ca measured preferably in the same direction as the cladding width W.sub.cl. The ratio between the cavity width W.sub.ca and the cladding width W.sub.cl, which is a direct ratio not to be confused with the duty ratio, is preferably about 0.4 to 1.8. The ratio shown in FIG. 2 is the preferred range of 0.6 to 1.6, which allows especially for high absorption rates for light in an infrared band. Furthermore, the cavity height h.sub.ca and the base height h.sub.r are shown in FIG. 2. The preferred range of the ratio between the cavity height h.sub.ca and the base height h.sub.r is about 0.01 to 0.5. Shown in FIG. 2 is the in particular preferred value of this ratio about 0.08 to 0.1. Furthermore, it is shown that beneath the reflector base there is arranged a substrate layer 7, which supports the structure as claimed by the current invention. It is to be understood that on top of the absorbing layer 4 additional layers, like an anti-reflection coating, can be arranged to improve the performance of the absorbing structure 1. These additional layers preferably directly contact the top surface 42 of the absorbing layer 4.
[0036] FIG. 3 shows a preferred embodiment of the cell structure 10 comprising an absorbing layer 104, a sequence of cavities 106 and a sequence of cavity claddings 126 arranged between these cavities 106. The cavity's claddings 126 are preferably part of the reflector 102. On top of the absorbing layer 104 there are arranged preferably two or several additional layers 8 to help to improve the absorption enhancement at the absorbing layer 104 and the reflector respectively the cavities 106 and 126. On its left side the cell structure 10 comprises electrical contacts to be connected to an electric wire receiving the electric current generated by the cell structure 10.
[0037] FIG. 4 shows a diagram illustrating the percentage of absorbed power in dependency of the wavelength of the incoming radiation. The different graphs are showing the absorbed power in the reflector 2 (labeled with AG), the absorbed power in the absorbing layer (SI) and the total amount of absorbed power (Total). This graph impressively shows that the reflector 2 made of silver has a very low amount of parasitic absorption while allowing very high values of percentage of absorbed power within a Silicon layer, which is current generating layer in a solar cell.
[0038] FIGS. 5a-5d clarify different preferred shapes of the cavity 6, which preferably is filled with cavity filler 62. On the upper left side there is shown a conical shape of the cavity 6, which in particular is preferred to utilize radiation of different polarization states. In another preferred embodiment, the cavity 6 and the cavity filler 62 might be shaped rectangular which allows high absorption rates for radiation of a certain polarization state and is easy to produce. On the lower left side a cylindrical cavity is shown while on the lower right side a cubic cavity shape is shown. The cylindrical shape is preferably symmetrical to a direction orthogonal to the lower side 24 of the reflector 2. Accordingly the cubic shape is symmetrical to two orthogonal planes, which furthermore are orthogonal to the lower side 24 of the reflector 2. The cubic and the cylindrical shape allow the absorption of light with different polarization states. The cylindrically shaped cavity shown on the lower left side is especially preferred when producing the reflector 2 according to the invention with lithography.
REFERENCE NUMERALS
[0039] 1structure [0040] 2, 102reflector [0041] 4, 104absorbing layer [0042] 6, 106cavity [0043] 7substrate layer [0044] 8additional layers [0045] 10cell structure [0046] 22upper side [0047] 24lower side [0048] 25reflector base [0049] 26, 126cavity cladding 42top surface [0050] 44bottom surface [0051] h.sub.cacavity height [0052] h.sub.rbase height [0053] W.sub.cacavity Width [0054] W.sub.clCladding Width
