Electronics

Breakthrough rectenna converts light into DC current

Breakthrough rectenna converts...
Georgia Tech engineers have taken advantage of nanoscale technologies to create an antenna able to capture and convert light into direct current
Georgia Tech engineers have taken advantage of nanoscale technologies to create an antenna able to capture and convert light into direct current
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Georgia Tech engineers have taken advantage of nanoscale technologies to create an antenna able to capture and convert light into direct current
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Georgia Tech engineers have taken advantage of nanoscale technologies to create an antenna able to capture and convert light into direct current
Associate professor Baratunde Cola observing a laser being used in his research on visible-light rectennas
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Associate professor Baratunde Cola observing a laser being used in his research on visible-light rectennas
The researchers cultivated an array of billions of vertically-aligned carbon nanotubes on top of a silicon substrate using chemical vapor deposition
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The researchers cultivated an array of billions of vertically-aligned carbon nanotubes on top of a silicon substrate using chemical vapor deposition
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Rectifying antennas – "rectennas" – are used as parasitic power capture devices that absorb radio frequency (RF) energy and convert it into usable electrical power. Constructing such devices to absorb and rectify at optical wavelengths has proved impractical in the past, but the advent of carbon nanotubes and advances in microscopic manufacturing technology have allowed engineers at the Georgia Institute of Technology to create rectennas that capture and convert light to direct electrical current. The researchers believe that their creation may eventually help double the efficiency of solar energy harvesting.

First created more than 40 years ago, rectennas have been used to capture and convert energy at various wavelengths as short as ten microns (in the infrared range), and have found use in such things as re-using localized RF energy to power near-field communications (NFC). However, researchers have been trying to create devices that operate at visible wavelengths with little success.

"The physics and the scientific concepts have been out there," said associate professor Baratunde Cola. "Now was the perfect time to try some new things and make a device work, thanks to advances in fabrication technology."

These advances enabled researchers to cultivate an array of billions of vertically-aligned carbon nanotubes on top of a silicon substrate using chemical vapor deposition. Each of these nanotubes is glazed with an aluminum oxide insulator, and the whole array is capped off with optically-transparent thin layers of calcium then aluminum to act as an anode.

The researchers cultivated an array of billions of vertically-aligned carbon nanotubes on top of a silicon substrate using chemical vapor deposition
The researchers cultivated an array of billions of vertically-aligned carbon nanotubes on top of a silicon substrate using chemical vapor deposition

The multiwall carbon nanotubes harness light energy by oscillating in response to the incoming optical radiation. This generates a charge that is then passed through inbuilt rectifiers, which convert alternating current into direct current. These rectifiers switch on and off in response to the oscillations at incredible speeds in the petahertz (one quadrillion times per second) range and "push" electrons across the uppermost electrode to create a small amount of direct current.

Despite the fact that these devices currently operate at less than one percent efficiency, the Georgia Tech engineers are working on optimization techniques they believe could greatly improve their performance and lead to practical application in solar technology.

Associate professor Baratunde Cola observing a laser being used in his research on visible-light rectennas
Associate professor Baratunde Cola observing a laser being used in his research on visible-light rectennas

"We could ultimately make solar cells that are twice as efficient at a cost that is ten times lower, and that is to me an opportunity to change the world in a very big way," said Cola. "As a robust, high-temperature detector, these rectennas could be a completely disruptive technology if we can get to one percent efficiency. If we can get to higher efficiencies, we could apply it to energy conversion technologies and solar energy capture."

The team outlines the research in the shortvideo below.

Theresults of this work were recently published in the journal Nature Nanotechnology.

Source:Georgia Institute of Technology

First Optical Rectenna Converts Light to DC Current

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8 comments
8 comments
Shadowmerlin
Interesting article. I especially like the statement at the end about the cost being "ten times lower". That's the most wonderful part - remember, a cost of only one times lower means the cost is zero. If it's ten times lower, that means they give us back 9 times what the cost used to be!
EH
Antennas for light could lead to the creation of optical phased array detectors, which get all the information from the light wave field in a way similar to a hologram. If a sphere were covered with 100nm (1/4 wave for blue light) optical antennas, it would be able to see in all directions simultaneously with the resolution of a telescope with a diameter almost as big as the diameter of the sphere. A ten meter sphere would act as tens of thousands of ten-meter telescopes. However, even with improvements in electronics, though processing such a flood of data would be very difficult. (I had this idea about 12 years ago.)
Bob Flint
Shadowmerlin" I interpreted it as something that cost $10 dollars is now only $1
Even at that if it's really twice as efficient then halve that and for 50 cents worth you can no get the power that originally cost $10 of material.
When will we see these benefits in production?
Don Duncan
When I see such predictions as "a cost that is 10 times lower" at such an early phase in research, I think, "Someone is looking for funding". Shark Tank would tell them: "Show us a lot more progress, e.g., come back when you have a solar collector twice as efficient at one tenth the cost.
S Michael
Don't hold your breath to this to be developed in the next 10 to 15 years if ever. Pie in the sky looking for funding from the taxpayer for vaporware. I do have one question. Why use nanotubes. Why not use carbon strands and make a larger array, that just might useful now. Just a thought.
abbiemary
Bara is a heck of a researcher, so I am very hopeful that he will be able to follow through with this. I worked with him at Purdue when he was getting his Ph.D. and he was able to plow through a variety of roadblocks. This is one invention that I have a great deal of hope in.......
westtx@1949
Cut antennas that resonate at frequencies above and below the visible light spectrum...especially in the Cosmic Ray band where the energy is detectable and convertible to DC even in mines deep underground. These phased array antennas that resonate in the spectrum above and below that of visible light could be added to light gathering arrays to supplement present day photovoltaic arrays. And, some parts of the spectrum are available 24 hours each day, not blocked by clouds or matter.
It should be possible to construct resonant antennae that resonates at neutrino frequencies and thus tap a heretofore untapped source of energy from all over the universe.
ol' Lawrence

ParishMatthewWolfe
I hate to break it to all of you... but Tesla did this in the 30's. Although it was written off as a hoax, it is clear that he reverse engineered radio broadcast waves into electricity. I'm going to build a large scale one, hook it to an electric car and drive for free while sucking all the cell signal and radio broadcasts right out of the air. Not really cause I'm poor but I would if i wasn't.