A solar concentrator device comprising a solar concentrator element comprising a radiation transmissive surface, a radiation absorptive material and a radiation concentrating/collection point and disposed on the incident radiation side thereof a recapture element for recapturing at least a portion of radiation lost from the concentrator element has improved solar radiation collection efficiency by reintroducing recaptured radiation into the concentrator element or by propagating said recaptured radiation through the recapture element to a radiation concentration point associated with the recapture element. It has been found that planar elements having a grooved or corrugated outer surface make for very good recapture elements for planar concentrator elements.