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Sometimes doping is good

One of the perpetual criticisms of solar power is the high cost versus traditional fossil fuel sources or nuclear power.  To be fair, these criticisms are largely true.  However, critics should keep an open mind about solar power as an energy source in the long run as exciting research is being done that could dramatically boost efficiencies and increase the power yield of solar cells, decreasing deployment costs.

I. Meet the Q-BIC 

Much recent work has revolved around "quantum dots" -- tiny metal and/or organic nanocrystals in the 1-20 nm range.  Quantum dots have unique properties and can actually produce more than one electron for every photon that hits them (a quantum efficiency > 100%) in a phenomenon called "multiple exciton generation" (MEG, for short).

Quantum dots
Quantum dots don't just look pretty, they have some handy physics quirks too!
[Image Source: Elec-Intro]

The latest breakthrough in quantum dots comes from the lab of Professor Vladimir V. Mitin at the University at Buffalo, New York.  Professor Mitin's new quantum dots harvest light in the infrared spectrum -- often underutilized in solar cells -- complementing existing photovoltaics.

But his special quantum dots do something more.  They're pre-doped with a negative charge, which helps them repel electrons.  Why would you want to repel electrons from your quantum dots?  

Well, imagine you have all your quantum dots exposed to visible light and they're busy "harvesting" the energy from the infrared portion of that light.  This "harvest" occurs by the infrared-range photons transferring their energy to an electron in one of the nanocrystal's atoms.  The electron is excited and "jumps" out of its orbit, joining a free flow current stream of electrons from various quantum dots.  The current flow is driven by a potential difference.

But imagine if one of the electrons in the stream passes by a quantum dot and sees one of the "holes" left when an excited electron departed.  It can sometimes fill in that empty space, in a phenomenon called recombination.  This is a bad thing, as all of a sudden your electrons go from producing useful current to malingering around in your nanocrystal.

By doping your nanocrystal, you're putting a lot of negative charge in it.  So even if your nanocrystal sheds some of its electron load, it's still has a lot of negatively charged electrons.  Like repels like, so this means electrons in the current stream tend to avoid the nanocrystals and recombination drops.

These special doped nanocrystal quantum dots are known as quantum dots with built-in-charge (Q-BICs).

Quantum Dot crystals
An electron micrograph of quantum dots (dark bumps in right most image) and an artist's sketch of a layered quantum dot cell (right images) are seen in this picture from an earlier Professor Mitin paper. [Image Source: Vladimir V. Mitin/University at Buffalo]

Professor Mitin didn't do this work alone.  The work was done by his core team, which also consisted of Andrei Sergeev and Nizami Vagidov, faculty members in UB's electrical engineering department; Kitt Reinhardt of the Air Force Office of Scientific Research; and John Little and advanced nanofabrication expert Kimberly Sablon of the U.S. Army Research Laboratory.

Professor Mitin isn't revealing the exact chemical stew used in the nanocrystalline Q-BICs, as he and his fellow professors have filed for a provisional patent on their work.  But his past studies [PDF] indicate that they're using indium arsenic nanodots, for at least some of their work.

III. What's Next

Professors Mitin, Sergeev, and Vagidov are joining together to found a startup company to market the solar cells, which they say can increase the conversion efficiency by 45 percent over traditional designs, between harvesting the infrared and fighting recombination of the infrared-derived current.  The new company is called OPtoElectronic Nanodevices LLC. (OPEN LLC.)

Eventually solar cells will likely make heavy use of quantum dots, as these little nanostructures allow high efficiency capture of targeted portions of the spectrum -- efficiency so high that it would violate the laws of physics if the nanocrystal was a traditional semiconductor.  By mixing nanodots, a cell could capture most of the visible light spectrum.  This latest development -- Q-BIC -- adds one more tool to improve such a design.
Quantum Dot mixture
A solar cell with a mixture of tuned quantum dots, perhaps doped Q-BICs would be a truly optimal third-generation solar cell.
[Image Source: Los Alamos Science & Tech Mag./U.S. Department of Energy's NNSA]

Solar may not win out in the long term with viable alternatives like nuclear fusion and algal biofuels on the way.  But developing efficient solar power will be a critical step for mankind in the creation of self-sustaining colonies on alien moons, asteroids, and worlds -- environments that often lack significant quantities of carbon and water (a source of fusion fuel) -- but that have an abundance of silicon and other mineral resources.

Source: University at Buffalo



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Just a question
By zombieX on 1/25/2012 1:55:46 PM , Rating: 3
The article lists the school, faculty, army and air force researchers. However, the blog continues on to state that some of those people are starting a company and have applied for a provisional patent.

Considering tax dollars were most likely the largest source of funding for this, how is that possible?

I know it's probably a naive question, but shouldn't the school (since those faculty members we're on the payroll) and the military have the major say in what happens with this invention.

Furthermore if tax dollars are/were being used shouldn't this be an open technology to benefit all. Let's be honest schools are largely funded by the tax payer anyway.

As I type this I realize it sounds a bit socialistic, but it really is a capitalistic idea. If we're going to fund and support these projects shouldn't we get something back. I know if I had a choice to invest my tax dollars I would expect a return on my investment if money was going to be made from research made possible largely due to my investment.




RE: Just a question
By drycrust3 on 1/25/2012 2:53:53 PM , Rating: 2
Not being an American, I would say it depends on the employment contract, but it stands to reason that the employment contract would state that inventions derived while employed at the school, university, research lab, branch of the government, whatever, belong to that place. In this case, as you say, the patents should be owned by the school and the branch of the military that paid for its development.


RE: Just a question
By zombieX on 1/25/2012 3:24:50 PM , Rating: 2
I would have to believe most employers would have such contracts. Most places I have worked have had clauses to cover inventions while on employer time at a minimum, most have covered even on your own time.

Can't believe I was rated down for asking a question. That is why I stopped posting here years ago. Too many people just like to rate for no good reason.


RE: Just a question
By drycrust3 on 1/25/2012 3:36:10 PM , Rating: 2
Don't take it too personally, sometimes people click the rating buttons by accident, and there isn't any way to correct it.
Another point is that an early poster can't rate a later comment.
As I said, don't take it too personally, that is just the opinion of a few. Look at someone like Tony, he must have the most -1s of anyone, and yet he keeps his head up and keeps putting down what he believes is right.
The important point is you expressed an opinion, and a good scientist who disagrees with you would present arguments as to why, which is a far better indication of where your arguments stand. If no one presents an alternative opinion, then maybe you are right.


RE: Just a question
By Fritzr on 1/25/2012 9:10:53 PM , Rating: 2
To answer your original question, it is called licensing.

Lets call this a government owned patent. The government now has the option of burying it, funding a government agency to manufacture or allowing a private manufacturer to produce the product. In the last case they can declare it public domain or accept royalty payments from companies that buy the license to produce the product.

These same choices apply to any owner of a patent. In this case it sounds like the inventors are forming a company that intends to manufacture this new type of photovoltaic under license. Whether it will be an exclusive license or not, they are still keeping quiet about details to make sure they have a lead when it goes to market.


RE: Just a question
By choadenstein on 1/25/2012 9:21:34 PM , Rating: 3
Responding as a patent attorney.

When you file a provisional patent application (or any patent application for that matter), the filing documents have a box to check if government funding was used in development of the invention.

Typically with government grants or the use of government personnel/funds, the US government is provided with a right to use the invention if one or more patent issues from the funded research without the requirement to pay any royalties.

Universities vary on policy, but one common policy for universities is to release inventions to the inventors (e.g., faculty, grad student, other personnel) if the university does not want to commercialize or otherwise pursue the invention.

I have no idea what the situation is in this case, but thought I would share those little bits of information.


"People Don't Respect Confidentiality in This Industry" -- Sony Computer Entertainment of America President and CEO Jack Tretton














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