It was noted that atomic H, produced at a hot wire, passivated bulk defects in polycrystalline material without damaging the surface. Solar cells made from such material responded much more favourably to hot-wire hydrogenation than to low-energy ion implantation or direct-current plasma treatment. Hot-wire passivation yielded a H concentration, close to the surface, of 8 x 1019/cm3 and improved the minority carrier diffusion length of solar cells by up to 100%. Implantation, as well as conventional plasma treatments, resulted in lower H concentrations and therefore in much smaller improvements in diffusion length.

Efficient Defect Passivation by Hot-Wire Hydrogenation. R.Plieninger, H.N.Wanka, J.Kühnle, J.H.Werner: Applied Physics Letters, 1997, 71[15], 2169-71