We examine the carrier lifetime evolution of block-cast multicrystalline silicon (mc-Si) wafers under illumination (100 mW/cm2) at elevated temperature (75°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°C. However, we detect only a weak lifetime instability in mc-Si wafers which are RTA-treated at 650°C. After completion of the degradation, the lifetime is observed to recover and finally reaches carrier lifetimes 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.

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Based on quasi-steady-state photoluminescence, we present an approach to extract minority carrier lifetime from silicon wafers without a priori information about any material parameter (e.g., dopant concentration or mobility). A sinusoidal oscillation of irradiation of a silicon sample in time stimulates a likewise oscillating excess carrier density. Our approach is based on the fact that - in the quasi-steady-state regime - the time shift between the maxima of irradiation intensity and the intensity of radiative recombination is linked to effective minority carrier lifetime. Exploiting the continuity equation, it is possible to determine injection dependent minority carrier lifetime from there