Hydrogen in silicon: diffusion and defect passivation

Results of studies on hydrogen diffusion and the passivation of crystal defects and impurities in single and polycrystalline silicon obtained from several different vendors are discussed. It is shown that enhanced diffusion of hydrogen can occur in some of these materials, both in the bulk and along grain boundaries, with an effective diffusivity of about an order of magnitude higher than previously reported values. Hydrogen incorporated for defect passivation can induce defects in silicon. These defects and their recombination characteristics are discussed, and it is proposed that these defects pose the ultimate limit on the degree of improvement manifested by a cell. A back-side hydrogenation technique for solar cell passivation is described