Black silicon refers to the apparent color of the surface of a silicon wafer after it has been etched with nano-scale pores; the black color results from the absence of reflected light from the porous wafer surface.
Natcores antireflective coating process begins with an uncoated, textured silicon wafer. First, nanoscale pores are etched into the wafer surface, using gold or silver nanoparticles, by submerging the wafer for a few minutes in a liquid solution at room temperature. Next, using the companys liquid phase deposition (LPD) process, Natcore scientists fill the pores and then over-coat them with silicon dioxide. This combination step both coats and passivates, thereby allowing lower reflectance.
NRELs most meaningful new black silicon patent relates to the use of copper nanoparticles in the etching process instead of nanoparticles of gold or silver.
Because copper is less expensive than the precious metals, this new patent could enable Natcore to further reduce the cost of solar cells, says Natcore President and CEO Chuck Provini. This could be another step toward our goal of halving the cost and increasing the output of solar cells.
Natcore scientists have created a black surface on a silicon wafer with an average reflectance in the visible and near-infrared region of the solar spectrum of 0.3%, making it the blackest silicon solar cell surface ever recorded. Natcore refers to this surface as Absolute Black.
The original NREL-Natcore license was granted in December 2011. Natcore and NREL have also entered into a Cooperative Research and Development Agreement to develop commercial prototypes that embody NRELs black silicon inventions.
NREL is the U.S. Department of Energys primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for DOE by the Alliance for Sustainable Energy LLC.
