Transparent conductive layer and method
The photovoltaic structure comprises a thin film coating on a transparent substrate, the thin film comprising an effective amount of nanocrystalline silicon embedded in a matrix of amorphous and/or microcrystalline silicon. A transparent conducting oxide layer on a layer of non-conductive transparent oxide provides light-trapping capability as well as electrical conductivity where needed. A chemical vapor deposition (“CVD”) reactor provides improved gas distribution to the substrates being coated in the reactor. An improved sputtering process and an improved RF plasma-enhanced CVD manufacturing method both using high levels of hydrogen in the hydrogen-silane mixture and high electrical power levels for the plasma to increase the speed and to lower the cost of manufacturing.
1. A support member transmissive to electromagnetic radiation comprising visible light,
(a) a first thin-film coating on one surface of said support member, said first coating comprising substantially pure zinc oxide in fiber texture form and having relatively low electrical conductivity, and which is transmissive to electromagnetic radiation comprising visible light, and;
(b) a second thin-film coating on said first coating, said second coating comprising zinc oxide transmissive to electromagnetic radiation comprising visible light, and doped to make it electrically conductive.
2. The structure of claim 1 wherein the upper surface of said first coating is etched.
3. The structure of Claim 1 wherein said second coating is doped with approximately 1.5% by weight aluminum.
4. The structure of claim 1 wherein said support member is comprised of glass and the thickness of said first coating is at least twice the thickness of said second coating.
5. The structure of claim 4 wherein said glass is selected from the group consisting of low-iron glass and soda lime glass.
6. The structure of Claim 1 wherein said first coating is between approximately 500 nm thick and approximately 750 nm thick.
7. The structure of claim 6 wherein said second coating is approximately 250 nm thick.
8. The structure of Claim 1 further comprising a thin-film coating of silicon dioxide on said one surface of said support member and underneath said first thin-film coating.
9. The structure of claim 8 wherein said aluminum comprises approximately 1.5% by weight of said second layer having a thin-film coating of silicon dioxide on the surface of said support member opposite said one surface.
10. The structure of claim 2 wherein the surface of said second coating is etched.
11. A support member transmissive to electromagnetic radiation comprising visible light,
(a) a first thin-film coating on one surface of said support member, said first coating comprising substantially pure zinc oxide in fiber texture form and having relatively low electrical conductivity, and which is transmissive to electromagnetic radiation comprising visible light, and;
(b) a second thin-film coating on said first coating, said second coating comprising zinc oxide transmissive to electromagnetic radiation comprising visible light, and doped to make it electrically conductive,
wherein said second coating has a plurality of recesses distributed over its surface.
12. The structure of claim 11 wherein said recesses comprise pits and holes, said pits and holes occupying an area of up to approximately 50% of the total area of said second coating.
13. The structure of claim 11 in which said recesses comprise through holes.
14. The structure of claim 1 in which said support member has an etched surface on which said first coating is formed.
15. The structure as in claim 14 in which the size of the surface irregularities is of the same order of magnitude as the wavelengths of light to be transmitted through said structure.
16. A structure as in claim 8 in which said support member has an etched surface on which said silicon dioxide coating is formed.
17. A support member transmissive to electromagnetic radiation comprising visible light,
(a) a first thin-film coating on one surface of said support member, said first coating comprising substantially pure zinc oxide in fiber texture form and having relatively low electrical conductivity, and which is transmissive to electromagnetic radiation comprising visible light, and;
(b) a second thin-film coating on said first coating, said second coating comprising zinc oxide transmissive to electromagnetic radiation comprising visible light, and doped to make it electrically conductive.
(c) said one surface of said support member being roughened,
(d) a thin-film coating of silicon dioxide on said one surface of said support member and underneath said first coating,
(e) the upper surface of said first coating being etched and having recesses, and
(f) said second coating comprising approximately 1.5% by weight of aluminum.
18. A structure as in claim 17 in which there is a second coating of silicon dioxide on the surface of said support member opposite said one surface.