Impurities and Metastable Centers in Amorphous Silicon Solar Cells

ABSTRACTAmorphous silicon solar cells are adversely affected by impurities through the creation of traps, recombination centers and metastable centers. The microstructure of discharged-produced, hydrogenated amorphous silicon (a-Si:H) appears to be strongly affected by the presence of impurities in the discharge atmosphere. A model is developed in which impurities create microvoids in a-Si:H, and traps, recombination centers and metastable centers are associated with the internal surfaces of the microvoids. In this model, hydrogen plays an important role in determining the electronic activity and diffusivity of impurities, and metastable centers are created by the trapping of holes near microvoids and the induced motion of hydrogen on the internal surfaces of the microvoids.