Solare Energie- und Systemforschung
Hrsg.: Fraunhofer ISE, Freiburg/Brsg.
2019, 210 S., num., mostly col. illus. and tab., Softcover
Freiburg, Univ., Diss., 2017
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Crystal defects substantially affect the properties of semiconductors. In silicon intended for photovoltaic energy conversion a crucial influence is the recombination of excess charge carriers introduced by defects. This thesis investigates properties of recombination-active crystal defects in monocrystalline silicon.
The prevalent production technique for monocrystalline silicon for photovoltaic application, the Czochralski crystallisation method, introduces large amounts of oxygen to the otherwise very pure monocrystalline silicon crystals. This gives rise to the formation of a group of defects.
This thesis investigates these oxygen-related defects. An experimental method is developed to illustrate and investigate the lateral distribution of interstitial oxygen Oi in silicon wafers. Oi is an important precursor for the formation of SiOx precipitates and an indicator for studies of complexes of boron and oxygen responsible for light-induced degradation LID. Detailed studies of the activation kinetics and the recombination activity of boron-oxygen-complexes are presented. The results are discussed and put into perspective in the framework of a literature review.
Further studies performed on oxygen-lean silicon grown by the float-zone method demonstrate that LID can also be caused by defects not related to oxygen contamination.