Influence of the addition of aluminum in boron-doped Cz-Si on degradation and regeneration kinetics

The impact of additional Al present in B-doped Cz-grown Si on the long-term behavior of excess charge carrier lifetime is investigated. From the resulting defect density and saturation current density j0, after a degradation a delayed onset of regeneration and a delayed increase of the j0 values can be observed in the material containing an order of magnitude more Al. The effect is less pronounced with constant injection as compared to constant generation conditions, but still significant and thus the causing effect seems to be injection-dependent. In addition to the time delay, a higher activation energy for the regeneration reaction can be determined. The effect of the delay could be shown not only for lifetime samples, but also for PERC solar cells. The developed model to explain the obtained findings is based on the assumption that due to the higher binding energy of Al-H pairs compared to B-H pairs, the release of H of the dopant-H complex is delayed and the regeneration reaction depends on this released H.