Light trapping optical cover

Abstract

A light trapping optical cover employing an optically transparent layer with a plurality of light deflecting elements. The transparent layer is configured for an unimpeded light passage through its body and has a broad light input surface and an opposing broad light output surface. The light deflecting elements deflect light incident into the transparent layer at a sufficiently high bend angle with respect to a surface normal and direct the deflected light toward a light harvesting device adjacent to the light output surface. The deflected light is retained by means of at least TIR in the system formed by the optical cover and the light harvesting device which allows for longer light propagation paths through the photoabsorptive layer of the device and for an improved light absorption. The optical cover may further employ a focusing array of light collectors being pairwise associated with the respective light deflecting elements.

1 . An optical cover for use atop a light harvesting device, comprising:
 a layer of optically transmissive material including a plurality of light deflecting means each configured to alter the transversal propagation direction of light incident onto said light harvesting device and communicate said light a generally greater propagation angle with respect to a surface normal than a pre-defined critical angle;   wherein the cumulative aperture of said light deflecting means is less than the area of said layer.   
     
     
         2 . An optical cover as recited in  claim 1 , wherein said predefined critical angle is an angle of a total internal reflection characterizing at least one surface of said layer. 
     
     
         3 . An optical cover as recited in  claim 1 , wherein each of said light deflecting means comprises at least one reflective surface inclined at an angle to a surface of said layer. 
     
     
         4 . An optical cover as recited in  claim 1 , wherein each of said light deflecting means comprises at least one refractive surface inclined at an angle to a surface of said layer. 
     
     
         5 . An optical cover as recited in  claim 1 , wherein each of said light deflecting means comprises a surface configured to reflect by means of a total internal reflection. 
     
     
         6 . An optical cover as recited in  claim 1 , wherein each of said light deflecting means comprises a surface relief feature selected from the group consisting of prismatic grooves, prismatic cavities, pyramidal cavities, and conical cavities. 
     
     
         7 . An optical cover as recited in  claim 1 , wherein each of said light deflecting means is selected from the group consisting of planar mirrors, curved mirrors, mirror arrays, prisms, prism arrays, one or more reflective or refractive surfaces, blind holes, through holes, undercuts, notches, surface discontinuities, discontinuities in said layer, surface corrugations, diffraction gratings, holograms, surface texture, light diffusing elements, and light scattering elements. 
     
     
         8 . An optical cover as recited in  claim 1 , wherein each of said light deflecting means has an elongated shape and is aligned generally parallel to a reference line. 
     
     
         9 . An optical cover as recited in  claim 1 , wherein said plurality of light deflecting means is arranged in a cylindrical configuration. 
     
     
         10 . An optical cover as recited in  claim 1 , wherein said plurality of light deflecting means is arranged in an axisymmetrical configuration. 
     
     
         11 . An optical cover as recited in  claim 1 , further comprising a plurality of light collecting elements optically coupled to said light deflecting means so that each pair of an individual light collecting element and an individual light deflecting means forms an individual opticule configured as a two-stage optical system in which said light collecting element collects light from its input aperture and focuses said light onto said deflecting means having a generally smaller aperture and configured to redirect the focused beam at a different angle compared to the incidence angle. 
     
     
         12 . An optical cover as recited in  claim 1 , further comprising a micro-lens array disposed in optical communication with said plurality of light deflecting means. 
     
     
         13 . An optical cover as recited in  claim 1 , further comprising a micro-lens array disposed in optical communication with said plurality of light deflecting means, wherein said lens array includes micro-lenses in either one of the cylindrical or point focus configuration. 
     
     
         14 . An optical cover as recited in  claim 1 , further comprising one or more optical cladding layers having a lesser refractive index than said layer of optically transmissive material. 
     
     
         15 . An optical cover as recited in  claim 1 , wherein said light harvesting device comprises a layer of photovoltaic material. 
     
     
         16 . An optical cover as recited in  claim 1 , wherein said light harvesting device comprises a layer of photovoltaic material and a layer of electroconductive transparent material. 
     
     
         17 . An optical cover as recited in  claim 1 , wherein said light harvesting device comprises a layer of photovoltaic material and a grid of electroconductive contacts. 
     
     
         18 . An optical cover as recited in  claim 1 , wherein said light harvesting device comprises a reflective surface. 
     
     
         19 . An optical cover as recited in  claim 1 , wherein said light harvesting device comprises one or more devices selected from the group consisting of solar cells or panels, radiation detectors, light absorbers, photo-chemical reactors and photo-bioreactors. 
     
     
         20 . A light harvesting device having a layered structure, comprising:
 a photoabsorptive layer configured to absorb incident light, and a layer of optically transmissive material having a broad-area surface and configured to transmit said light into said photosensitive layer and trap said light within said light harvesting device by means of at least a total internal reflection from said surface.