Feedstock recharging during directional solidification of silicon ingots for PV applications

Beier M, Trempa M, Seebeck J, Reimann C, Wellmann P, Gründig-Wendrock B, Friedrich J, Dadzis K, Sylla L, Richter T (2015)

Publication Language: English

Publication Type: Conference contribution

Publication year: 2015

Pages Range: 717-721

Conference Proceedings Title: Proceedings of the 29th EU PVSEC conference

Event location: Amsterdam NL

ISBN: 3-936338-34-5

DOI: 10.4229/EUPVSEC20142014-2AV.1.11

Abstract

Directional solidification (DS) is a well-established crystallization technology to produce polycrystalline or quasi-mono crystalline silicon ingots for photovoltaic applications. Before the crystallization process the silica crucible is charged with irregular shaped silicon feedstock typically resulting in a filling degree of 50 to 60%. Hence, the grown silicon ingot is only about the half of the available crucible height or volume, respectively. The upper part of the crucible cannot be used for crystallization which means considerable yield losses. One approach to overcome this problem is the recharging of new silicon feedstock (solid or liquid state) into the melt during crystallization. In this work the effects of the recharging processes on the crystal growth behavior and the material properties were investigated. At the beginning the immersion behavior of the silicon feedstock into the silicon melt was simulated by model experiments where polyethylene granules were dropped into water. Afterwards some growth experiments in a modified G1-DS-furnace were carried out. The recharging process was done with 10 kg of different feedstock types leading to a 60% increase of ingot height from 130 to 210 mm. After crystallization the grain structure and the specific resistivity of the silicon ingots were investigated. The results show that the contact of the recharged feedstock particles with the solid liquid interface has necessarily to be avoided to grow high quality silicon ingots by this technology. Additionally it could be demonstrated that recharging of undoped feedstock during the crystallization process has the potential to flat the resistivity gradient over the ingot height.

Authors with CRIS profile

Peter Wellmann Professur für Werkstoffwissenschaften (Werkstoffe der Elektrotechnik)

Involved external institutions

Fraunhofer-Institut für Integrierte Systeme und Bauelementetechnologie (IISB) DE Germany (DE)

How to cite

APA:

Beier, M., Trempa, M., Seebeck, J., Reimann, C., Wellmann, P., Gründig-Wendrock, B.,... Richter, T. (2015). Feedstock recharging during directional solidification of silicon ingots for PV applications. In EUPVSEC (Eds.), Proceedings of the 29th EU PVSEC conference (pp. 717-721). Amsterdam, NL.

MLA:

Beier, Maximilian, et al. "Feedstock recharging during directional solidification of silicon ingots for PV applications." Proceedings of the 29th European Photovoltaic Solar Energy Conference and Exhibition, Amsterdam Ed. EUPVSEC, 2015. 717-721.

BibTeX: Download