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Grain boundaries and dislocations in Si-bricks: Inline characterization on as-cut wafers

: Strauch, T.; Demant, M.; Krenckel, P.; Riepe, S.; Rein, S.

Fulltext ()

Energy Procedia 124 (2017), pp.806-813
ISSN: 1876-6102
International Conference on Crystalline Silicon Photovoltaics (SiliconPV) <7, 2017, Freiburg>
Journal Article, Conference Paper, Electronic Publication
Fraunhofer ISE ()
PV Produktionstechnologie und Qualitätssicherung; Photovoltaik; Silicium-Photovoltaik; Charakterisierung von Prozess- und Silicium-Materialien; Messtechnik und Produktionskontrolle; dislocations; boundaries; quality; silicon; high-performance

In High-Performance mc-Si [1] random grain boundaries, although being recombination active, often enhance material quality by reducing dislocations. With this work, we take a step towards statistical large-scale investigations of crystal defects via a combined analysis of different inline-measurements on as-cut wafers: photoluminescence images for the extraction of recombination-active structures and reflection and infrared transmission images for the extraction of the grain structure. The combined extraction of recombination-active structures and grain structures allows isolating dislocations from grain boundaries for all material types. To discern dislocations from other recombination-active defect structures, an image-processing-based analysis technique has been developed. By applying this separation on wafers from various bricks of our material set, typical developments of grain structure and dislocations can be identified. As a particular application, we investigat e the correlation between the development of dislocations in higher parts of the brick and grain size in the lower parts. The results support theory quantitatively: Dislocation ratio in the upper brick part shows a correlation with the square root of the weighted median of the grain size in the lower brick part (R â 0.85). However, the results also show that grain size distribution, in particular grain size homogeneity, has to be considered to account for a stronger distinction between materials.