Daniel Skorka

Bio: Daniel Skorka is an academic researcher from University of Konstanz. The author has contributed to research in topics: Passivation & Sputtering. The author has an hindex of 8, co-authored 22 publications receiving 256 citations.

Degradation and regeneration in mc-Si after different gettering steps

Abstract: Light and elevated temperature induced degradation (LeTID) affects significantly the performance of multicrystalline (mc) Si passivated emitter and rear cell (PERC) solar cells, and underlying mechanisms of LeTID are still unknown. In this work LeTID and following regeneration of an industrial mc-Si PERC solar cell is compared to differently processed minority charge carrier lifetime samples under illumination (1 sun) and elevated temperature (75 °C). LeTID on cell level reveals the same kinetics compared to lifetime samples. Varying the processing sequence has a significant effect on LeTID of lifetime samples. Ungettered samples with fired SiNx:H surface passivation show a very strong LeTID and regeneration effect, with degradation kinetics being similar for all wafer areas irrespective of initial material quality. In contrast, regeneration sets in earlier in good quality areas. Differently gettered samples with lower contamination level than ungettered samples are less sensitive to LeTID, while overall degradation and regeneration behavior is strongly influenced by applied gettering sequences. Al-gettered samples show a more pronounced degradation effect than P-gettered samples, leading to the assumption that P-gettering is more effective in the reduction of LeTID sensitive defects. If the gettering step is less effective, in lifetime samples after degradation a beginning regeneration effect could be observed. A model is presented, describing LeTID in boron as well as gallium doped mc-Si being based on impurities that can be gettered and redistributed during high temperature steps. Using this experimental approach helps to clarify the underlying mechanisms of LeTID and leads to a better understanding of degradation and regeneration mechanisms in mc Si. Copyright © 2016 John Wiley & Sons, Ltd.

Degradation of Surface Passivation on Crystalline Silicon and Its Impact on Light-Induced Degradation Experiments

Abstract: A decrease of surface passivation quality is observed in FZ, Cz, and mc-Si lifetime samples during light-induced degradation (LID) treatments. It is shown that this degradation occurs not only in samples with single SiN x :H layers but also when using layer stacks consisting of SiO x /SiN x :H or AlO x :H/SiN x :H. Time-resolved calculation of the surface saturation current density J 0 s is shown to be a reliable method to separate changes in the bulk and at the surface of samples during LID treatments. The impact of the observed changes in passivation quality on the outcome and interpretation of LID experiments aiming at changes in the bulk of Cz or mc-Si is investigated and discussed.

Evaluating root cause: The distinct roles of hydrogen and firing in activating light- and elevated temperature-induced degradation

Abstract: The root cause of light- and elevated temperature-induced degradation (LeTID) in multicrystalline silicon p-type passivated emitter and rear cell (PERC) devices is still unknown. Microwave-induced remote hydrogen plasma (MIRHP) is employed to vary the concentration of bulk hydrogen and to separate the effects of hydrogen and firing temperature in LeTID-affected wafers. We find that hydrogen is required for degradation to occur, and that samples fired prior to the introduction of hydrogen do not degrade. Importantly, samples with hydrogen that have not been fired do degrade, implying that the firing time-temperature profile does not cause LeTID. Together, these results suggest that the LeTID defect reaction consists of at least two reactants: hydrogen and one or more defects that can be separately modified by high-temperature firing. We assess the leading hypotheses for LeTID in the context of our new understanding of the necessary reactants.The root cause of light- and elevated temperature-induced degradation (LeTID) in multicrystalline silicon p-type passivated emitter and rear cell (PERC) devices is still unknown. Microwave-induced remote hydrogen plasma (MIRHP) is employed to vary the concentration of bulk hydrogen and to separate the effects of hydrogen and firing temperature in LeTID-affected wafers. We find that hydrogen is required for degradation to occur, and that samples fired prior to the introduction of hydrogen do not degrade. Importantly, samples with hydrogen that have not been fired do degrade, implying that the firing time-temperature profile does not cause LeTID. Together, these results suggest that the LeTID defect reaction consists of at least two reactants: hydrogen and one or more defects that can be separately modified by high-temperature firing. We assess the leading hypotheses for LeTID in the context of our new understanding of the necessary reactants.