Dry Epitaxial Lift-Off for High Efficiency Solar Cells

A new method of transferring epitaxially grown active films onto an inexpensive polymeric flexible carrier. Specifically, for making thin lightweight high efficiency (> 30%) IMM3J solar cells while reusing the GaAs or Ge base wafer. This will reduce the costs of fabricating high efficiency PV cells by 30% and will raise specific power to > 200W/kg. The method uses a thin strained layer under the epitaxially grown active layers without ion implantation or wet etching. A crack propagates in the strained layer splitting the epi-layers from the base wafer after bonding to polyimide wafer, hence dry epitaxial lift-off (DELO), due to the difference in thermal expansion coefficients between the semiconductor and flexible substrate without applying mechanical pressure. The base wafer is re-used to grow new epi-layers.