SPLTRAK Abstract Submission
Hydrogen complexes present after different firing profiles and their influence on LeTID degradation
Benjamin Hammann1, Nicole Assmann2, Philip M. Weiser2, Wolfram Kwapil1,3, Tim Niewelt1,3,4, Florian Schindler1, Rune Søndenå5, Eduard V. Monakhov2, Martin C. Schubert1
1Fraunhofer Institute for Solar Energy ISE, Freiburg, Germany
/2Centre for Materials Science and Nanotechnology, Department of Physics, University of Oslo, Oslo, Norway
/3Laboratory for Photovoltaic Energy Conversion, Department of Sustainable Systems Engineering (INATECH), University of Freiburg, Freiburg, Germany
/4School of Engineering, University of Warwick, Coventry, United Kingdom
/5Institute for Energy Technology, Kjeller, Norway

The influence of the cooling rate during the fast-firing process and of the sample thickness on the initial hydrogen (complex) distribution in p- and n-type silicon wafers is investigated using low-temperature Fourier Transform-Infrared (FT-IR) spectroscopy. The impact of the introduced hydrogen on the formation of defects during dark annealing and light soaking is then studied by resistivity and charge carrier lifetime measurements. We observe a lower overall hydrogen concentration for thinner wafers or slower cooling rates. This is especially pronounced for the concentration of the hydrogen molecule H2A. We observe a weak signature of light- and elevated-temperature-induced degradation (LeTID) during dark annealing accompanied by a significant increase in BH pair concentration. Interestingly, the extent of degradation does not correlate with the chosen process variations. Regeneration of the carrier lifetime occurs earlier in thinner wafers and in fast-fired samples. During light soaking, the LeTID extent clearly correlates with the initial hydrogen (H2A) content, while the BH pair formation appears to be suppressed. In addition to H2A and BH-pairs, the dark annealing experiments indicate that at least one more source of hydrogen is present in the initial wafers.