Kinetics of hydrogenation and interaction with oxygen in crystalline silicon

Sufficient passivation of recombination active defects in the bulk of crystalline silicon solar cells using atomic hydrogen is a key feature for reaching high conversion efficiencies. This is of special interest for promising low-cost multi-crystalline (mc) materials, as a substantial cost reduction concerning Watt-peak(Wp)-costs seems to be possible. The effectiveness of this hydrogenation is strongly influenced by the diffusion kinetics of atomic hydrogen in silicon. Oxygen impurities seem to play a major role, as they have the ability to trap hydrogen, slowing down the diffusion of hydrogen atoms. For two crystalline silicon materials the influence of different oxygen concentrations on hydrogen kinetics is discussed. We demonstrate that not only the overall oxygen concentration, but as well the thermal history of the samples has to be taken into account. Precipitation of oxygen alters the diffusion kinetics and has an influence on vacancy concentration. Faster passivation of crystal defects can be reached in low-oxygen samples.