[111] oriented silicon, when etched with NaOH at 80C produces texture at the material surface.

N doped silicon heat treated develop oxynitride nanofeatures (precipitates and voids covered with nanometer thick oxynitride layer) in the near surface region.  When etched these leave a finely textured surface that causes the observed extremely low reflectance.

 

Only a small amount of light escapes from the bulk and forms a boundary layer of diffuse light, and which couples with the textured surface.

N doped silicon processed to produce extremely fine nanostructure at the surface that results in low reflectance.

 

This work was sponsored by NREL and the former photovoltaic company Astropower/GE.  The process was integrated in Astropower solar cell production line.