Berlin 2015 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 14: Crystallization, Nucleation and Self Assembly II (joint session CPP, DY)
CPP 14.8: Talk
Monday, March 16, 2015, 18:00–18:15, PC 203
Phase field simulations of particle capture during directional solidification of photovoltaic silicon — Heike Emmerich1, •Henning Hörstermann1, Julia Kundin1, Jochen Friedrich2, Maral Azizi2, Christian Reimann2, Arne Cröll3, Thomas Jauß3, and Tina Sorgenfrei3 — 1University Bayreuth, Chair of Material and Process Simulations, Bayreuth, Germany — 2Fraunhofer IISB, Erlangen, Germany — 3University Freiburg, Institute for Geosciences, Freiburg, Germany
We study the interaction between the solidification front and SiC particles present in the melt during the growth process of silicon for solar cells. Particles of a given size are pushed in front of the interface for growth velocities below a critical value and are incorporated into the crystal for growth velocities above this value. The existing theoretical models for particle capture find a relationship between critical particle size and critical growth velocity by assuming an equilibrium between a combination of gravity, drag, lift and other forces acting on the particle in the vicinity of the interface. For silicon these models predict significantly higher critical particle sizes than observed in experiments. We use a phase field model to test if these deviations can be explained by deviations from the spherical particle shape usually assumed in the theoretical models or effects like the deformation of the interface caused by the presence of the particle. In addition to testing and adapting existing theories, we narrow down the possible underlying mechanisms by identifying relevant length scales and other properties that are required to explain the experimental results.