Lifetime degradation and regeneration in multicrystalline silicon under illumination at elevated temperature

We examine the carrier lifetime evolution of block-cast multicrystalline silicon (mc-Si) wafers under illumination (100 mW/cm(2)) at elevated temperature (75 degrees C). Samples are treated with different process steps typically applied in industrial solar cell production. We observe a pronounced degradation in lifetime after rapid thermal annealing (RTA) at 900 degrees C. However, we detect only a weak lifetime instability in mc-Si wafers which are RTA-treated at 650 degrees C. After completion of the degradation, the lifetime is observed to recover and finally reaches carrier life-times comparable to the initial state. To explain the observed lifetime evolution, we suggest a defect model, where metal precipitates in the mc-Si bulk dissolve during the RTA treatment. (C) 2016 Author(s).