| As an expert on silicon and solar, the technology is doomed- here's why: •It is totally possible, in terms of the physics, to do what they're proposing. All you have to do is take your ingot or boule of FZ or Cz Silicon, draw a vacuum on it, backfill it with hydrogen, and run your ion implantation head over it. Like a Durandal bomb, the upper surface is relatively undisturbed but a cutting effect occurs beneath the surface. Pop, off comes your perfect and thin wafer. •This idea has been proposed before. •There's nothing fundamentally wrong with a 3 micron thick silicon wafer. It takes some different processing steps to trap the light, but you can still make a decent solar cell out of it. It's not better than a 400 micron wafer in terms of efficiency, but not much worse. Also, by it being so thin, it's flexible and not so darn brittle. That reduces breakage but also makes handling a little more challenging. •The idea fails when you consider the economics. First consider the market you're trying to break into- there's a huge glut of silicon wafer manufacturing capacity in the industry. Silicon manufacture is going gang busters, so it's not a commodity that's expensive to begin with. Solyndra bet on silicon prices staying high and that, more than any other reason, is why they failed. This is the same bet with a different topology. •Bill Nye should perform a little math problem- consider the amount of electricity and hydrogen gas necessary to perform a cleave, 100% efficient, 100% yield, and multiply these quantities by their respective commodity costs. You will end up with a number in excess of the cost of a 500 micron wafer, or perilously close to one. •I did the math five years ago and it made no sense then, when silicon wafers sold for over twice as much. Just because the existing technology is materially wasteful (it definitely is, generating a lot of kerf and going through a lot of expensive wiresaw blades and polishing processes) doesn't mean that it's economically wasteful. It's not too late to pivot- I'm sure he'll have no difficulty raising the money in spite of these shortcomings. I'd be more than happy to steer this company in the right direction, contributing IP that actually delivers on these promises. All it takes is an e-mail. |
- The "magic," if anything, is supposed to be that super-thin kerfless wafers could justify the industrial scale use of float zone silicon. FZ has often been the material of choice for lab scale fabrication of champion devices. Unlike ordinary boron doped p-type Cz silicon, it doesn't have dissolved oxygen traces from crucible walls, so it doesn't suffer B-O complex light induced degradation.
- High efficiency is still worth a premium, even if low-mid range quality cells are stuck in a brutal commoditized competition. (But high efficiency is not worth a large premium, hence the problems of even well-established high efficiency manufacturers like SunPower and Panasonic.)
- Super thin wafers are less sensitive to bulk recombination. Though this theoretical advantage is unneeded if you're starting with superpure FZ silicon in the first place.
- FZ silicon is only available in smaller diameters, so the cells wouldn't be drop-in replacements in the usual 60/72 cell module that starts with 156 mm cells.
- Silicon's resistance to damage by cosmic rays goes up dramatically as the cell thickness drops down to the few-tens-of-microns range. But that's not relevant for terrestrial use and compound semiconductors are still more efficient and more damage-resistant for space use.
Other companies that proposed to do kerfless wafering with ion implantation and failed to reach commercial success:
Twin Creeks Technologies
GT Advanced Technologies (later owners of Twin Creeks assets)
SiGen
1366 Technologies appears to have the closest-to-industrial kerfless process at present, though it's not as dramatic as as some kerfless technology concepts. I hope that their partnership with Hanwha Q Cells goes to full scale production before the money runs out.