Abstract: A photovoltaic solar cell comprises a piece of semiconductor material incorporating a p-type region, an n-type region, a p-n junction between the two, electrodes contacting the two regions, and within its body a lattice defect denuded zone and a lattice defect gettering zone.The defect gettering zone may be a precipitate-rich zone or a region of lattice damage. The denuded zone may include the p-n junction.The semiconductor material may be Si, GaAs or InP.Methods for making the solar cell are described, involving heat treatment steps to produce a denuded zone, nucleating precipitates and generating precipitates. Alternatively precipitation may be nucleated, or a lattice damage zone may be generated, by proton bombardment.