We numerically calculate the spectral reflectivity of the silicon nitride (Si3N4) sub-wavelength structure (SWS) using a two-dimensional finite element simulation. The geometry-dependent effective reflectance of the Si3N4 SWS over the wavelength ranging from 400 nm to 1000 nm is examined and the structure of Si3N4 SWS is further optimized for the lowest effective reflectance. A p–n junction solar cell efficiency based on the optimized Si3N4 SWS is also calculated, resulting in an improvement of 0.98% in efficiency than that of single layer antireflection coatings.
