NOVELTY - Photovoltaic assembly (10), comprises: photovoltaic cell (20) having light incident surface and mounting surface on it; array of conductive lines (22) being disposed over light incident surface; optical element (40) having a body (42) including first and second opposed, substantially planar major surfaces on it, where first surface defines light incident surface and second surface defines light output surface; and a layer of adhesive material having an index of refraction (nA) disposed between light output surface of optical element and light incident surface of photovoltaic cell.    USE - Used as a photovoltaic assembly.    ADVANTAGE - The photovoltaic assembly has lower induced absorbance rate, thus exhibits improved radiation durability.    DETAILED DESCRIPTION - Photovoltaic assembly (10), comprises: a photovoltaic cell (20) having a light incident surface and a mounting surface on it; an array of conductive lines (22) being disposed over the light incident surface, where each conductive line has 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 (40), having a body (42) including first and second opposed, substantially planar, major surfaces on it, where the first surface defines a light incident surface and the second surface defines a light output surface, the light output surface has many grooves formed in it, each groove having a mouth opening on the light output surface, where the mouth has a predetermined width dimension 'b' measured in the plane of the light output surface, and each groove having opposed, substantially planar boundary walls that extend into the body and terminate within them at a closed apex, where the closed apex has an included apex angle alpha ; and a layer of an adhesive material having an index of refraction (nA) disposed between the light output surface of the optical element and the light incident surface of the photovoltaic cell, where the layer of adhesive material has an index of refraction and has a thickness dimension 't', the thickness dimension 't' being so that the adhesive layer covers all of the grid lines of the array. The optical element is positioned with respect to the photovoltaic cell so that 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 is improved in that it is operative to collect light incident upon the light incident surface at an incident angle beta up to a maximum operating angle beta 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 or to convey that light to the light output surface by the mechanism of total internal reflection from the boundary walls of the grooves present within the body of the optical element. In the improved optical element, the body is formed from a material having an index of refraction (nc) of at least 1.3 and an induced absorbance rate Delta Abs/Dose of less than or equal to 0.4, the index of refraction (nA) is in the range of 1.34-1.5, and the planar boundary walls of the grooves are coated with a reflective material, where the angle alpha is any one of the relationships, as given in the specifications.    DESCRIPTION OF DRAWING(S) - The figure shows stylized section view of a photovoltaic assembly that comprises an optical element attached through an adhesive layer to the light incident surface of a photovoltaic solar cell.    Photovoltaic assembly (10)    Photovoltaic cell (20)    Array of conductive lines (22)    Optical element (40)    Body (42)