Solar-Grade Silicon from Metallurgical-Grade Silicon Via Iodine Chemical Vapor Transport Purification

T. F. Ciszek, T. H. Wang, M. R. Page, R. E. Bauer, M. D. Landry

Research output: Contribution to conferencePaperpeer-review

5 Scopus Citations


In an atmospheric-pressure "open" reactor, SiI2 transfers from a hot (>1100°C) Si source to a cooler (>750°C) Si substrate and decomposes easily via 2SiI2 → Si + SiI4 with up to 5μm/min deposition rate. SiI4 returns to cyclically transport more Si. When the source is metallurgical-grade Si, impurities can be effectively removed by three mechanisms: (1) differing free energies of formation in forming silicon and impurity iodides; (2) distillation; and (3) differing standard free energies of formation during deposition. Distillation has been previously reported. Here, we focused on mechanisms (1) and (3). We made feedstock, analyzed the impurity levels, grew Czochralski single crystals, and evaluated crystal and photovoltaic properties. Cell efficiencies of 9.5% were obtained. Incorporating distillation (step 2) should increase this to a viable level.

Original languageAmerican English
Number of pages4
StatePublished - 2002
Event29th IEEE Photovoltaic Specialists Conference - New Orleans, LA, United States
Duration: 19 May 200224 May 2002


Conference29th IEEE Photovoltaic Specialists Conference
Country/TerritoryUnited States
CityNew Orleans, LA

Bibliographical note

For preprint version including full text online document, see NREL/CP-520-31443

NREL Publication Number

  • NREL/CP-520-33687


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