16.8% Efficient Ultra-Thin Silicon Solar Cells on Steel

This paper reports on an 18 um silicon solar cell. Silicon for this solar cell is grown on porous Si so it can be separated and layer transferred. This ultra-thin silicon is transferred to and integrated with a steel substrate. The National Renewable Energy Laboratory confirms this solar cell’s efficiency of 16.8%, the highest efficiency found for any silicon solar cell under 40 um, either free-standing or on a foreign substrate. We describe the design, modeling and fabrication of this solar cell.