Patent ID: 8236266

Claim:
A method for forming high quality silicon material for photovoltaic devices substantially free from oxygen containing impurities, the method comprising: transferring a raw silicon material and a plurality of carbon species in a crucible having an interior region, the crucible being made of a quartz material, the quartz material being capable of withstanding a temperature of at least 1400° C.; subjecting the raw silicon material in the crucible to thermal energy to cause the raw silicon material to be melted into a liquid state to form a melted material at a temperature of greater than about 1400° C., the melted material having an exposed region bounded by the interior region of the crucible; subjecting an exposed inner region of the melted material to an energy source comprising an arc heater configured above the exposed region and spaced by a gap between the exposed region and a muzzle region of the arc heater to cause formation of a temperature profile within a vicinity of an inner region of the exposed melted material while maintaining outer regions of the melted material at a temperature below a melting point of the quartz material of the crucible; maintaining the crucible during the subjecting of the exposed inner region of the melted material to the energy source in a substantially motionless state such that an outer region of the melted material is substantially free from a mixing action; maintaining a resulting oxygen concentration within the exposed inner region to a concentration using at least the substantially motionless state of the crucible; causing an interaction between at least one of the carbon species and at least two of an oxygen species from the resulting oxygen concentration to form a gaseous carbon dioxide; removing the gaseous carbon dioxide from the exposed inner region of the melted material, the removing of the gaseous carbon dioxide species occurring in an upward manner via a venting device to prevent remixing of the gaseous carbon dioxide species with a portion of the melted material, the venting device having a V-shaped path and including a horizontal reflecting part, a plurality of guiding grooves, and a plurality of lateral grooves coupled to the guiding grooves, the guiding grooves being coupled to the horizontal reflecting part: and removing one or more other impurities from the melted material to form a higher purity silicon material in the crucible; wherein the substantially motionless state is provided between a boundary between the inner region of the crucible and the outer region of the melted material such that the boundary is substantially free from the mixing action.