Systematic analysis of trapping as a tool to predict diffusion length in multicrystalline silicon cells

In this work we show that there is an inverse correlation between trap density in the as-cut wafer and effective diffusion length in the solar cell for regions with high trap densities, but a positive correlation for regions with low trap densities. We also present strong hints that traps are strongly correlated to oxygen and that iron and molybdenum can attenuate the trapping effect. So far trapping of minority carriers has been assumed to cause this anomalous increase of lifetime, but the effect could also be explained by Depletion Region Modulation (DRM) at defects. Temperature dependent experiments have been performed to clarify the origin of the anomalous increased lifetime.