Patent ID: 8802477

Claim:
A method for forming a heterojunction III-V photovoltaic (PV) cell, the method comprising: forming a first intrinsic layer on a substrate; forming a first back surface field layer on the first intrinsic layer; forming a first amorphous silicon layer on the first back surface field layer; performing a layer transfer of a base layer from the substrate, the base layer having a thickness of less than about 20 microns, wherein the layer transfer comprises spalling, and wherein spalling comprises: forming a metal layer having a tensile stress on the first amorphous silicon layer; adhering a flexible substrate to the metal layer; using the tensile stress in the metal layer to cause a fracture in the wafer below the base layer, wherein a location of the fracture and the thickness of the base layer are determined by the tensile stress and a thickness of the metal layer; and removing the flexible substrate from the metal layer; forming a second-intrinsic layer on the base layer; forming a second-amorphous silicon layer on the second intrinsic layer; and forming a transparent conducting oxide layer on the second amorphous silicon layer.