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.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC36-99-GO10337
- OSTI ID:
- 15006973
- Report Number(s):
- NREL/CP-520-31443; TRN: US200412%%542
- 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
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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
QUANTUM EFFICIENCY
SOG-SI FEEDSTOCK
REFINING/SUBLIMATION
THERMO-DECOMPOSITION
SOLAR ENERGY - PHOTOVOLTAICS