Effect of solute hydrogen on toughness of feedstock polycrystalline silicon for solar cell applications

Three commercial polysilicon materials (1 mm–1 cm granular beads) produced from different fluidized bed reactors were examined to determine the relationship between solute hydrogen and toughness. Infrared spectroscopy was used to identify hydrogen, and indentation was used to determine mechanical properties. Annealing the beads decreased solute hydrogen and increased toughness by 20%, from 0.74 to 0.97 MPa m1/2. However, annealing also increased the crystallite size by as much as 50%, which can lower the toughness.