Welding helmets (Hobby use)

The silicon used in thin-film cells typically is doped, or nucleated with hydrogen. These typically wind up being nanocrystalline materials as they're applied to a specific task.
But as-deposited amorphous silicon has no detectable cystal structure, at any scale. The standard diffraction method for detecting amorphous materials may be ambiguous at nanoscales, but there is no *positive* indicator for crystal structure in pure amorpous silicon.
Reply to
Ed Huntress
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This disagrees:
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"By high resolution transmission electron microscopy (HRTEM) it was found that the average size of crystals in samples deposited in that way were similar, about 8-9 nm, whereas crystal size distributions were generally broad and varied for different samples."
The crystalline structure may simply have been undetectable with your friend's equipment back in the 1980's.
In the 60's the analysis of crystals by X-Ray diffraction needed a dedicated round room with film or detectors at precisely positionable locations on the walls. Constructive interference from the regularly spaced atoms in crystal structures focuses the X-rays into spots on the wall like a prism. Amorphous material just creates diffuse fog.
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-jsw
Reply to
Jim Wilkins
I think there are still amorphous solar cells around. The solar cells in calculators were pretty much all amorphous cells. Cheap, not too efficient, but adequate for calculators.
Dan
Reply to
dcaster
Yes, looking around, I see that's one place where they're still used. There also are a variety of experimental multi-layer thin-film cells that contain a layer of amorphous silicon, and which have much higher efficiency. Sony has made some, and there is a large installation of them at an agriculture station somewhere in NJ.
The problem Sony had with theirs, initially, was relatively short life. I don't know if that's still the case.
Reply to
Ed Huntress
WAIT a minute. That paper is about hydrogen-doped amorphous/nanocrystalline silicon. It's been known for decades that doping with hydrogen causes amorphous silicon to adopt a nanocrystalline structure.
If that's the evidence, then I think the jury is still out on pure amorphous silicon.
Reply to
Ed Huntress
Yep, there are many observations we can't explain because we can't yet measure well enough at the atomic level, especislly below the surface.
That's why I objected to your blanket statement that amorphous silicon has no nanocrystals, in practical mass production versus by theoretical definition. I suspect the solar panel makers don't waste the time and money to check for them, and I once built semiconductor automatic test equipment for Teradyne and was a lab tech at Unitrode.
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My amorphous Harbor Freight panels will barely reach 0.6A instead of the 0.86A they are rated for. When I bought them I didn't have the test equipment to measure their maximum power point so I don't know if they met spec even then. No one offered a better kit at a local store.
The surplus monocrystalline panels have degraded in reverse leakage current but not output. At noon they were pushing 85W into the battery according to the power meter.
-jsw
Reply to
Jim Wilkins
No crystal shape but a crystal. Likely a translation from xxxx to English.
And missed.
Some experimentalist make it out of plastic and other materials.
Martin
Reply to
Martin Eastburn

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