Group thinks its ‘black silicon’ boosts photoconductive gainPublished on November 3rd, 2008 | By: firstname.lastname@example.org
Why settle for one photon when you can get 200-300? That’s the idea behind a new material being developed by SiOnyx, a new Massachusetts company. The company using a method to reshape the surface of silicon to create cones that it says makes the material effectively function as “sponge for light.” is making a new type of silicon material, dubbed black silicon, which captures nearly all of the sun’s light. The makers also claim that material provides reduced weight.
SiOnyx’s technology was developed and is licensed from Harvard University, also claims that the material makes it possible to use less silicon for light sensors, making the devices cheaper, smaller, and lighter.
Another way to look at the material is that it creates a very light-sensitive detector. Thus, besides PV applications, it could find its way into a number of different applications.
“If you have a very high-sensitivity detector, you could lower the radiation dose of x-rays to get that image,” says Stephen Saylor, company CEO. Saylor also suggests in-vitro imaging, night-vision optics and improved digital cameras.
From MIT’s Technology Review:
“Black silicon extends the technology that we know extremely well and makes it usable in a region of spectrum where it wasn’t useful before,” says Eric Mazur, a professor of applied physics at Harvard, who discovered the material in his lab. “I really believe it’s a new class of materials, just as semiconductors were a new class of materials 60 years ago.”
Mazur’s technique begins with ordinary silicon. Put it in a chamber full of sulfur hexafluoride gas, and pulse it with a femtosecond laser. This roughens the surface by creating millions of tiny cones on it. The rough layer is about 300 nanometers thick and infused with sulfur atoms.
This resulting cone-covered 300 nm thin layer does the trick, compared to the .5-mm used in many other PV applications.
The are still some questions about how exactly the material functions, but a leap in the silicon-sulfur material’s light absorbtion ability/photoconductive gain is where researchers are placing their hunch.
“We believe this is really the first time photonic gain has been seen in silicon,” Saylor says.
SiOnyx has yet to demonstrate a working PV application and acknowledges both technical and fabrication hurdles remain, but remain optimistic.
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