Silicon oxynitride films are grown by plasma-enhanced chemical vapour deposition on single-crystal Si(100) and textured Si solar cells, using a safe organic precursor, hexamethyl-disilazane. Using the Lucovsky-Phillips criterion of bond coordination constraints, we grow high-quality thin (~20 Å) and thick (up to 2700 Å) films which are carbon free (<1.0{%}) as characterized by x-ray photoemission spectroscopy (XPS) and Auger electron spectroscopy depth profiles. Core-level and valence band XPS is used to conclusively identify oxynitride bonding and band gap reduction in SiOxNy. For a λ/4 'blue' anti-reflection coating on the solar cells with uniform thickness (870± 15 Å) and composition (SiO1.6± 0.1N0.3± 0.05), an efficiency (AM 1) increase of 1{%} is obtained
