Heterojunction III-V photovoltaic cell fabrication

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.