Optimization of a-SiOx/a-SiNx Double Layer Antireflection Coatings for Silicon Solar Cells

Abstract

In this work we present an optimization of single- and double layer antireflection coatings (ARCs) for silicon solar cells. The wavelength-dependent reflectance and absorptance in the layers were calculated from experimental optical data measured on silicon nitride (a-SiNx:H) and oxynitride (a-SiOxNy:H) films deposited by plasma enhanced chemical vapour deposition with a wide range of compositions. Double layer ARCs were then designed by optimizing the thickness and composition of the layers with respect to both the total integrated reflectance weighted against the solar spectrum and the photogenerated current. Even though our double layer ARC can reduce the total reflectance from a polished Si surface under glass below 1.7%, an increased absorption in the ARC compensates some of this improvement. For moderately absorbing layers the relative photocurrent improvement from changing from a single layer ARC to a double layer ARC is ~1% under glass and ~2% in air. The improvement of cell efficiency may however be further increased by the enhanced passivation qualities of the more Si-rich layers.