Electrical, optical and structural investigation of low-temperature PECV-deposited hydrogenated amphorous silicon-oxynitride films for surface passivation of crystalline silicon solar cells

Abstract

Amorphous silicon oxynitride (a-SiOxNy:H) films, which are deposited by plasma enhanced chemical vapor deposition (PECVD) at low temperatures (Tdep < 200°C), are investigated in terms of their electrical, optical, and structural properties. The purpose is to develop a passivation layer for crystalline silicon solar cells, which is comparable to amorphous silicon (a-Si:H) films in terms of manufacturing process and passivation quality, but superior to a-Si:H films in terms of parasitic absorption. In comparison to a-Si:H films, amorphous silicon oxynitride films suffer less from parasitic absorption over the whole wavelength range due to their higher optical band gap (Eg). The widening of the optical band gap is realized by the incorporation of oxygen and nitrogen atoms in the amorphous network. Ongoing with the incorporation of oxygen and nitrogen atoms is the possibility to tune the refractive index (n) in a certain range, which turns amorphous silicon oxynitride into a very interesting material for solar cell applications, in particular for heterojunction solar cells and multilayer anti reflection coatings.