Method of cleaving a single crystal substrate parallel to its active planar surface and method of using the cleaved daughter substrate

A method of cleaving off a daughter single crystal substrate from a parent single crystal substrate includes providing a stress-mandrel and the parent a single crystal substrate. The parent single crystal substrate has a major surface and an edge surface that intersects the major surface. The major surface extends along a major surface plane. The stress-mandrel has a stress-mandrel coefficient of thermal expansion that is higher than the parent single crystal coefficient of thermal expansion. The method includes bonding the stress-mandrel to the major surface, and cooling the parent single crystal substrate and the stress-mandrel. The cooling of the parent single crystal substrate bonded to the stress-mandrel provides a thermal stress in the parent single crystal substrate sufficient to cleave the parent single crystal substrate. The cleaving extends substantially along a plane parallel to the plane of the major surface. In one embodiment the cleaved daughter substrate was used to make a photovoltaic cell.