Methods and Apparatuses for Manufacturing Geometric Multicrystalline Cast Silicon and Geometric Multicrystalline 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 geometrically ordered multi-crystalline silicon may be formed that is free or substantially free of radially-distributed impurities and defects and having at least two dimensions that are each at least about 10 cm is provided.

1 . A method of manufacturing cast silicon, comprising:
 placing a geometric arrangement of a plurality of silicon seed crystals on at least one surface in a crucible having one or more side walls heated to at least the melting temperature of silicon and at least one wall for cooling;   placing molten silicon in contact with the geometric arrangement of monocrystalline silicon seed crystals; and   forming a solid body comprising geometrically ordered multi-crystalline silicon, optionally having at least two dimensions each being at least about 10 cm, by cooling the molten silicon to control crystallization, wherein the forming includes controlling a solid-liquid interface at an edge of the molten silicon during the cooling so as to move in a direction that increases a distance between the molten silicon and the at least one wall for cooling.   
     
     
         2 . A method of manufacturing a solar cell, comprising:
 providing a body of cast silicon according to  claim 1 ;   forming at least one wafer from the body;   optionally performing a cleaning procedure on a surface of the wafer;   optionally performing a texturing step on the surface;   forming a p-n junction;   optionally depositing an anti-reflective coating on the surface;   optionally forming at least one layer selected from a back surface field and a passivating layer; and   forming electrically conductive contacts on the wafer.   
     
     
         3 . A method of manufacturing cast silicon, comprising:
 arranging a plurality of silicon seed crystals in a predetermined pattern on at least two surfaces of a crucible having one or more side walls heated to at least the melting temperature of silicon and at least one wall for cooling;   placing molten silicon in contact with the plurality of monocrystalline silicon seed crystals; and   forming a solid body comprising geometrically ordered multi-crystalline silicon, optionally having at least two dimensions each being at least about 10 cm, by cooling the molten silicon from the at least two surfaces of the crucible to control crystallization, wherein the forming includes controlling a solid-liquid interface at an edge of the molten silicon during the cooling so as to move the interface in a direction that increases a distance between the molten silicon and the monocrystalline silicon seed crystals in the crucible.   
     
     
         4 . A method of manufacturing cast silicon, comprising:
 placing a geometric arrangement of a plurality of silicon seed crystals on at least one surface in a crucible;   placing silicon feedstock in contact with the plurality of silicon seed crystals on the at least one surface;   heating the silicon feedstock and the plurality of silicon seed crystals to the melting temperature of silicon;   controlling the heating so that the plurality of silicon seed crystals does not melt completely, the controlling comprising maintaining a ΔT of about 0.1° C./min or less, as measured on an outside surface of the crucible, after reaching the melting temperature of silicon elsewhere in the crucible; and, once the plurality of seed crystals are partially melted,   forming a solid body comprising geometrically ordered multi-crystalline silicon by cooling the silicon.   
     
     
         5 . A method of manufacturing a solar cell, comprising:
 providing a body of cast silicon according to  claim 4 ;   forming at least one wafer from the body; optionally performing a cleaning procedure on a surface of the wafer;   optionally performing a texturing step on the surface;   forming a p-n junction;   optionally depositing an anti-reflective coating on the surface;   optionally forming at least one layer selected from a back surface field and a passivating layer; and   forming electrically conductive contacts on the wafer.   
     
     
         6 . A method of manufacturing cast silicon, comprising:
 arranging a plurality of silicon seed crystals in a predetermined pattern on at least two surfaces of a crucible;   placing silicon feedstock in contact with the plurality of silicon seed crystals on the at least two surfaces;   heating the silicon feedstock and the plurality of silicon seed crystals to the melting temperature of silicon;   controlling the heating so that the plurality of silicon seed crystals does not melt completely, the controlling comprising maintaining a ΔT of about 0.1° C./min or less, as measured on an outside surface of the crucible, after reaching the melting temperature of silicon elsewhere in the crucible; and, once the plurality of seed crystals are partially melted,   forming a solid body comprising geometrically ordered multi-crystalline silicon by cooling the silicon.   
     
     
         7 . A method of manufacturing a solar cell, comprising:
 providing a body of cast silicon according to  claim 6 ;   forming at least one wafer from the body;   optionally performing a cleaning procedure on a surface of the wafer;   optionally performing a texturing step on the surface;   forming a p-n junction; optionally depositing an anti-reflective coating on the surface;   optionally forming at least one layer selected from a back surface field and a passivating layer; and   forming electrically conductive contacts on the wafer.   
     
     
         8 . A method of manufacturing cast silicon, comprising:
 placing at least one geometric multi-crystalline silicon seed crystal on at least one surface in a crucible having one or more side walls heated to at least the melting temperature of silicon and at least one wall for cooling;   placing molten silicon in contact with the at least one seed crystal; and   forming a solid body comprising geometrically ordered multi-crystalline silicon, optionally having at least two dimensions each being at least about 10 cm, by cooling the molten silicon to control crystallization, wherein the forming includes controlling a solid-liquid interface at an edge of the molten silicon during the cooling so as to move in a direction that increases a distance between the molten silicon and the at least one geometric multi-crystalline silicon seed crystal in the crucible.   
     
     
         9 . A method of manufacturing a solar cell, comprising:
 providing a body of cast silicon according to  claim 8 ;   forming at least one wafer from the body;   optionally performing a cleaning procedure on a surface of the wafer;   optionally performing a texturing step on the surface;   forming a p-n junction;   optionally depositing an anti-reflective coating on the surface;   optionally forming at least one layer selected from a back surface field and a passivating layer; and   forming electrically conductive contacts on the wafer.   
     
     
         10 . A method of manufacturing cast silicon, comprising:
 placing a geometric arrangement of a plurality of silicon seed crystals on at least one surface in a crucible, the plurality of silicon seed crystals arranged to cover an entire or substantially an entire area of the at least one surface in the crucible;   placing molten silicon in contact with the geometric arrangement of silicon seed crystals; and   forming a solid body comprising geometrically ordered multi-crystalline silicon, optionally having at least two dimensions each being at least about 10 cm, by cooling the molten silicon to control crystallization.