Mechanism(s) of hydrogen diffusion in silicon solar cells during forming gas anneal

Surface damage in a silicon wafer, produced by mechanical polishing or ion implantation, is shown to mediate diffusion of hydrogen from a molecular ambient such as a forming gas. Experimental results show that the formation of a N/sup +/ region of a solar cell can produce significant surface stress similar to mechanical polishing. Results of hydrogen diffusion produced by forming gas annealing of various commercial photovoltaic silicon substrates and cells are discussed.