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Monday 10 March 2008, 10:30 PM
Silicon balls drop in zero G for solar cell magic
What do you think happens when you dribble molten silicon at thousands of droplets per second through a 14 metre tube? Rather magically, thousands of highly efficient, highly tiny, very spherical solar cells are created.
During the fall, the droplets form perfect spheres around a millimetre across - it's just the same as being in orbit, because they're free-falling, so surface tension pulls them into shape - and they've crystallised by the time they hit bottom. The minute cells pour out of the base of the fab like so many grains of sand.
Because they're circular, they absorb light all the way around. Slap a couple of wires on and encase them en-masse in glass: the resultant blobs can be put in front of a reflector, and the whole ensemble reaches 17 percent efficiency. That's good.
Each ball produces around 1.5 milliwatts, which isn't much in our terawatt society but is plenty for lots of low-power electronic applications - and each long-drop production tube makes watts-worth per second.
Kyoto company Kyosemi are the clever kids behind this particular piece of photovoltaic physics, and you can find a few more details in this page of the Semiconductor International website.
It's just a shame that you don't actually need an orbiting production line to make cool zero-gee semiconductors. They promised us factories in space - we get long thin tubes in Kyoto.
Ah well.
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