NOVELTY - The collector assemblage (30) has a transparent solid secondary optical element (SOE) (31), a solar cell (36) and a transparent material e.g. silicone denser than air between the SOE and the solar cell. A surface of the SOE facing the solar cell has an optically active region through which light passes to the solar cell, and which extends further towards the solar cell than an adjacent portion of the surface. The transparent material extends over the optically active region and portion of adjacent portion of the surface of the SOE.    USE - Collector assemblage for photovoltaic concentrator (claimed) e.g. solar concentrator used in photovoltaic solar electric systems.    ADVANTAGE - Since the transparent material extends over optically active region in surface of secondary optical element and portion of adjacent portion of that surface, more silicone is applied than necessary even to the point of completely encapsulating the area around the solar cell so that additional electrical insulation and environmental protection can be provided for the solar cell. An additional advantage of having an SOE with no defined alignment edges is that the special added features of avoiding the trapping of air or other gases between the SOE and silicone and enabling bubbles initially trapped in the silicone layer to be moved out of the optically active area of the SOE before the silicone is set can be easily employed. A distinct advantage to using a silicone fluid is that silicone can be a one-portion material, requiring no mixing, which eliminates the need to degas the silicone and reduces the introduction of bubbles into the process of applying the silicone and the assembly of the SOE onto the solar cell. The interference with the light from bubbles in a transparent medium in the optical path between a secondary optical element and a photovoltaic cell is thus eliminated or significantly reduced. Thus the optical performance and longevity of collector photovoltaic systems can be improved while at the same time assembly and assembly costs of the secondary optical element onto a multi-junction photovoltaic cell can be simplified and reduced.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a photovoltaic concentrator; and    (2) a method of making a collector assemblage for a photovoltaic concentrator.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view illustrating an axial section through the secondary optical element of a segmented Fresnel RR solar concentrator.    Collector assemblage (30)    Secondary optical element (31)    Air bubbles in silicone layer (32)    Silicone layer (33)    Solar cell (36)