Patent ID: 8648248

Claim:
A photovoltaic assembly comprising: a photovoltaic cell having a light incident surface and a mounting surface thereon, an array of conductive lines being disposed over the light incident surface, each conductive line having a predetermined line width substantially equal to a width dimension “g”, adjacent conductive lines in the array being separated from each other by a pitch dimension “p”; an optical element, the optical element having: a body having first and second opposed, substantially planar, major surfaces thereon, the first surface defining a light incident surface, the second surface defining a light output surface, the light output surface having a plurality of grooves formed therein, each groove having a mouth opening on the light output surface, the mouth having a predetermined width dimension “b” measured in the plane of the light output surface, each groove having opposed, substantially planar boundary walls that extend into the body and terminate therewithin at a closed apex, the closed apex having an included apex angle α, a layer of an adhesive material having an index of refraction n A disposed between the light output surface of the optical element and the light incident surface of the photovoltaic cell, the layer of adhesive material having an index of refraction n A and having a thickness dimension “t”, the thickness dimension t being such that the adhesive layer covers substantially all of the grid lines of the array, the optical element being positioned with respect to the photovoltaic cell such that substantially all of the conductive lines on the light incident surface of the cell lie within a respective groove formed on the light output surface of the optical element, the optical element being improved in that it is operative to collect light incident upon the light incident surface thereof at an incident angle β up to a maximum operating angle β Max measured with respect to a normal to the incident surface and to convey that light to the light output surface without retro-reflection toward the incident surface, the improved optical element being characterized in that: the body is formed from a material having an index of refraction n C of at least 1.3 and an induced absorbance rate ΔAbs/Dose less than or equal to about 0.4, and wherein the index of refraction n A is in the range from about 1.34 to 1.50, and wherein the angle α is defined in accordance with the relationship: α ≤ α Retro = 60 ⁢ ° - 2 3 ⁢ sin - 1 ⁡ ( sin ⁢ ⁢ β Max n C ) for any maximum operating angle β Max within the range 1°<β Max <90°; and wherein the dimension b lies within the range g + 2 ⁢ t ⁢ ⁢ sin ⁢ ⁢ β Max n A 2 - sin 2 ⁢ β Max = b Min 0 < b < b Max = p .