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Print 14 comment(s) - last by ssj3gohan.. on Jan 27 at 5:21 AM

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.


Hmmm
By NellyFromMA on 1/25/2012 3:20:41 PM , Rating: 2
Just curious, but I always wondered...

If we start capturing large majorities of concentrated sunlight (photons) in various spectrums, will plants and other lifeforms suffer from lack of this natural sunlight exposure?

I also wondered to a somwhat lesser extent if we start created large wind farms at various altitudes, will we be hindering and dissrupting the natural windcycles that carry hot and warm air to various climates? Don't we risk potentially putting to much of a 'load' on these systems? Systems meaning the wind and sunlight.

I know that's somewhat out there, but I'm still curious what the effects would be.




RE: Hmmm
By kwrzesien on 1/25/2012 3:46:42 PM , Rating: 2
I don't think our current effect is even close to the scale of the globe. But I wonder too where this would end up if someday we had millions of windmills and solar panels covering every village, town and city.

I also wonder what the effect of driving 1 (or 5 someday) billion cars can have - not just emissions but the combined heat released. Does it even register on the scale of heat from sunlight absorbed by the planet? Is it measurable compared to the change due to greenhouse gases?

Now get all 1 billion cars to accelerate from 0 to 60 pointing East at exactly the same time. Did the rotational speed of the planet feel a nudge?


RE: Hmmm
By drewsup on 1/26/2012 5:34:55 PM , Rating: 2
In other news..
Kid with bucket and spade drains ocean..

Window fans change the jet stream..

Ocean going vessels change the course of warm water currents..

I think you can sleep safely, entropy is alive and well..


What a useful invention!
By drycrust3 on 1/25/2012 1:28:26 PM , Rating: 3
quote:
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).

As I understand electromagnetic radiation, the frequency or wavelength of the radiation is energy dependent, much akin to the idea of electron-volts in atomic research. Thus, it takes more energy to a produce visible light photon than it does to produce an infra-red photon, and it takes more energy still to produce an ultra-violet photon than it does to produce a visible light one.
That means when a photon lands in a photon to electron convertor one shouldn't be surprised if more than one electron is produced.
That said, I think this is a real breakthrough for several reasons, one of which is it shows how inefficient our current range of photon-electron converters are.
This has some really interesting applications, such as a fridge that doesn't run off the mains, or a means to help charge up the battery in an electric car by parking outside in the sunshine while shopping at your local supermarket.




RE: What a useful invention!
By Etsp on 1/25/2012 8:02:18 PM , Rating: 2
I'm still not sure how that information relates to Verizon's iPhone sales numbers linked in that text (in the article)...


Yeah but
By YashBudini on 1/25/2012 1:54:02 PM , Rating: 3
While solar electricity efficiency is widely published what kind of efficiency can be obtained from solar heat collection? Suppose in the winter one wants to augment home heating and in the summer augment hot water heating?

And startup costs are pretty much basic materials.




By tharik on 1/25/2012 5:19:56 PM , Rating: 2
Well along with this research most of the medicines we use came from our tax dollars as well in the universities. when a drug gets close to completion in the academic world it is swept up by a drug company so they can patent it and then charge outrageous prices to the government that paid for it in the fist place. all with our tax dollars.

pretty cool isn't it.




Fun fact: solar isn't expensive
By ssj3gohan on 1/27/2012 5:21:21 AM , Rating: 2
Here's a fun fact: because of the huge increase in production of solar panels in the last 3 years or so (more than 30% bare panel cost reduction per year), combined with the recession, the price of solar panels has absolutely plummeted lately. This article starts with the assertion that photovoltaic power is expensive, but this is an outdated notion. It hasn't gotten much media attention, but PV panels are now actually at grid parity for some countries (like my own, the Netherlands). And they're set to drop a further 30% over the course of 2012, becoming as expensive as fossil fuel in parts of the US as well.

We're there, it's the future! No more hiding behind the argument that PV is expensive, because it isn't anymore. We're at $1/Wp right now, and we will be at $0.70/Wp by the end of the year.




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