Predicted electronic properties of polycrystalline silicon from three-dimensional device modeling combined with defect-pool model

Abstract

We assess a broad range of published experiments to show that the density of states (DOS) at high-energy grain boundaries in silicon is appropriately described by the defect-pool model. This implies that the DOS of such grain boundaries depends strongly on the dopant density and on the position of the Fermi level during device processing. However, since high-energy grain boundaries consist of an amorphous layer that is confined to a width of a few angstroms, the DOS is "frozen in" after material processing and does not suffer the strong degradation effects commonly observed in bulk a-Si:H. By combining three-dimensional device modeling and the defect-pool model, we reproduce various test structures and polycrystalline thin-film Si solar cells considerably more precisely than in the past. Our simulation model potentially provides a link between processing conditions and grain boundary quality.