Solid-phase crystallization of evaporated silicon thin films on glass for photovoltaics: A combined SEM and TEM study

The material-quality limiting factors of evaporated solid-phase crystallized (SPC) poly-Si thin films fabricated on planar glass for photovoltaic applications are investigated by a study combining scanning electron microscopy and transmission electron microscopy. The grains in the investigated thin films are found to be randomly oriented, with an average grain size of ~2.1 μm. In general, the grains are found to have a high defect density, although some grains are more defective than others. We also observe a high level of impurity incorporation, in particular, oxygen, into the film. The optical activity of the Si films is dominated by deep band tail states. We conclude that the high intragrain defect densities and the high impurity levels are two major limiting factors for obtaining high-quality evaporated SPC poly-Si thin films for photovoltaics.