By adding new patents to its original license to Natcore Technology Inc., the National Renewable Energy Laboratory (NREL) has expanded that license under which Natcore will develop and commercialize a line of black silicon products based on NREL patents.

• “Black silicon” refers to the apparent color of the surface of a silicon wafer after it has been etched with nano-scale pores.
• The new black silicon patent relates to the use of copper nanoparticles in the etching process instead of nanoparticles of gold or silver.

“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.

Natcore’s 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 company’s 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.

NREL’s most meaningful new black silicon patent relates to the use of copper nanoparticles in the etching process instead of nanoparticles of gold or silver.

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 NREL’s black silicon inventions.