Methods and apparatus for manufacturing monocrystalline cast silicon and monocrystalline cast silicon bodies for photovoltaics

Abstract

Methods and apparatuses are provided for casting silicon for photovoltaic cells and other applications. With such methods and apparatuses, a cast body of monocrystalline silicon may be formed that is free of, or substantially free of, radially-distributed impurities and defects and having at least two dimensions that are each at least about 35 cm is provided.

1 . A system for producing a monocrystalline ingot, comprising:
 a crucible provided in a furnace, the crucible configured to receive a single seed crystal and feedstock material;   at least one heating element for heating and at least partially melting the seed crystal, and completely melting the feedstock material contained in the crucible; and   a heat exchanger for controlling heat extraction from the crucible, in order to promote growth of the monocrystalline ingot from the at least partially melted seed crystal and the feedstock material;   wherein the heat exchanger is configured to promote cooling and directional solidification of the monocrystalline ingot.   
     
     
         2 . The system of  claim 1 , wherein the crucible includes a retainer for holding the crucible in the furnace. 
     
     
         3 . The system of  claim 1 , wherein the heat exchanger is operable in a plurality of stages to control a rate of melting of the seed crystal in the crucible. 
     
     
         4 . The system of  claim 1 , further comprising a probe or thermocouple to monitor melting of the feedstock material and meltback of the seed crystal. 
     
     
         5 . The system of  claim 1 , wherein the feedstock material is a polycrystalline silicon feedstock. 
     
     
         6 . The system of  claim 1 , wherein the heat exchanger is a gas-cooled heat exchanger. 
     
     
         7 . The system of  claim 1 , further comprising a heat exchanger block for supporting the crucible. 
     
     
         8 . The system of  claim 1 , wherein a shape of the crucible is one of a rectangular, conical, or tapered shape. 
     
     
         9 . The system of  claim 1 , wherein the crucible has a seed well portion for securing the seed crystal during monocrystalline growth. 
     
     
         10 . The system of  claim 1 , further comprising a support structure provided with the crucible for controlling heat flow.