Photochemical vapor-deposited silicon oxynitride films for solar cells

Abstract

Silicon oxynitride films (SiNXOY) were deposited at deposition temperatures between 100 and 300°C using mercury-sensitized photochemical vapor deposition. The light source was a low-pressure mercury lamp and the source gas was a mixture of NH3 gas and 5 percent SiH4 gas (95 percent N2 gas). The quality and interface property of these films were better than those of plasma-CVD films. However, in the former films, the film quality was unstable and degraded rapidly with time when the deposition temperature was low. Electron spectroscopy for chemical analysis (ESCA) indicated that the invasion of oxygen from air to the film caused a change in the film composition, resulting in the degradation of film property with time. The photochemical vapor deposition and plasma-vapor deposition SiNXOY films were used as an antireflective coating for a single-crystal-Si solar cell; and it was found that using the former films, the short-circuit current density and effective conversion efficiency were higher than by using the latter films. The difference in the foregoing results was believed to be due to the improvement of the interface property by photochemical deposition films.