Periodic silicon nitride-metamaterials structure for enhanced solar cell efficiency

Optical performance of photovoltaic solar cells and modules is mainly affected by the significant reflection losses at the air/glass front interface. To overcome this drawback, several antireflection coating materials on solar glass have been introduced as a mechanism for light trapping. Generally, materials employed as antireflection coating are SiO
₂
, TiO
₂
, ZnO and SiN
_x
. We propose in this study to minimize the reflection at the air/glass interface by n-binary unit cell silicon nitride-metamaterial antireflective structures on glass. For this purpose, we apply the effective medium theory that permits to simplify a layered structure to a single slab of homogeneous material. We utilize the Transfer Matrix Method to derive the reflectivity for both normal and Transverse Magnetic polarized light. With an appropriate choice of the refractive indices and the thicknesses of the silicon nitride layer and the metamaterial layer, the reflectivity is found not exceed 2.5% for the 7-binary unit cell structure.