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

This conference paper describes the atmospheric-pressure in an ''open'' reactor, SiI2 transfers from a hot (>1100C) Si source to a cooler (>750C) Si substrate and decomposes easily via 2SiI2 Si+ SiI4 with up to 5?m/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.
Authors:
; ; ; ;
Publication Date:
OSTI Identifier:
15006973
Report Number(s):
NREL/CP-520-31443
TRN: US200412%%542
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Conference
Resource Relation:
Conference: Conference title not supplied, Conference location not supplied, Conference dates not supplied; Other Information: PBD: 1 May 2002; Related Information: Prepared for the 29th IEEE PV Specialists Conference, 20-24 May
Research Org:
National Renewable Energy Lab., Golden, CO (US)
Sponsoring Org:
US Department of Energy (US)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; ATMOSPHERIC PRESSURE; DEPOSITION; DISTILLATION; HEAT EXCHANGERS; IMPURITIES; IODIDES; IODINE; MONOCRYSTALS; PURIFICATION; SILICON; SUBSTRATES; TRANSPORT; SOLAR ENERGY PV; ATMOSPHERIC-PRESSURE; SOLAR GRADE SILICON; CHEMICAL VAPOR TRANSPORT PURIFICATION; THIN-LAYER SI; CRYSTAL GROWTH; IMPURITIES; QUANTUM EFFICIENCY; SOG-SI FEEDSTOCK; REFINING/SUBLIMATION; THERMO-DECOMPOSITION; SOLAR ENERGY - PHOTOVOLTAICS