Efficient defect passivation by hot-wire hydrogenation

Atomic hydrogen, produced at a hot wire, passivates bulk defects in polycrystalline silicon without damaging surface regions. Solar cells from such polycrystalline silicon respond much more favorably to hot-wire hydrogenation than to low-energy ion implantation or a direct-current plasma treatment. Hot-wire passivation yields a hydrogen concentration close to the surface of 8×1019 cm−3 and improves the minority carrier diffusion length of solar cells by up to 100%. Implantation as well as conventional plasma treatment result in lower hydrogen concentration and, consequently, in much smaller improvements of diffusion lengths.