Thin Silicon Sheets for Solar Cells

Abstract

A thin layer of single-crystal silicon is produced by forming first trenches in a silicon substrate having (111) orientation; forming narrower second trenches at the base of the trenches; anisotropically etching lateral channels ( 4 ) from the second trenches, until adjacent etch fonts ( 16 ) substantially meet; and detaching said layer from the substrate. The trenches may be arranged so that the resultant layer has rows of slots, with the slots in adjacent rows being mutually offset. Solar cells may be formed on strips having two electrical contacts on the same face ( 6 ) of each strip ( 5 ).

1 . A sheet of silicon of (111) orientation or near (111) orientation and having a thickness of up to about 100 microns, said sheet comprising a plurality of parallel rows of slots therethrough, each of said rows containing a plurality of said slots arranged endwise therein, wherein the slots in each row are offset with respect to slots in an immediately adjacent row. 
     
     
         2 . The sheet of silicon according to  claim 1  wherein said slots have a length of at least 3.33 times a spacing between adjacent rows of slots. 
     
     
         3 . A solar cell comprising a sheet of silicon according to  claim 2 . 
     
     
         4 . A silicon solar cell comprising a strip of silicon having a length of at least 20 mm, a width of up to about 5 mm, and a thickness of up to about 0.1 mm, and further comprising contact regions on one face of said silicon solar cell for respective p and n metal contacts. 
     
     
         5 . The silicon solar cell according to  claim 4  having a length of more than about 50 mm, a width of up to about 2 mm, and a thickness of up to 70 microns. 
     
     
         6 . The sheet of silicon according to  claim 1  further comprising lateral channels extending from the slots, wherein said lateral channels undercut a surface of said sheet of silicon. 
     
     
         7 . The sheet of silicon according to  claim 1 , wherein a surface of a silicon substrate of said sheet of silicon is at an angle of from 0 to 10 degrees from the (111) orientation or the near (111) orientation.