Method of Making Thin Silicon Sheets for Solar Cells
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 having a thickness of up to about 100 microns, said sheet including 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 the slots in an immediately adjacent row.
2 . A 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 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 having a pair of electrical contacts on one face of said solar cell.
5 . A 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.