Q-BICs -- Doped Quantum Dots -- Harvest Wasted Infrared Solar Spectrum
January 25, 2012 11:04 AM
comment(s) - last by
Sometimes doping is good
One of the perpetual criticisms of solar power is the high cost versus traditional fossil fuel sources or
. 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 "
" -- tiny metal and/or organic
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 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
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).
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
[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.
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
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.
University at Buffalo
This article is over a month old, voting and posting comments is disabled
Considering tax dollars were most likely the largest source of funding for this, how is that possible?
1/25/2012 5:19:56 PM
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.
"Google fired a shot heard 'round the world, and now a second American company has answered the call to defend the rights of the Chinese people." -- Rep. Christopher H. Smith (R-N.J.)
Apple's iPhone Outsells All Android Phones Combined at Verizon
January 24, 2012, 4:18 PM
U.S. is Only 3 Years Behind China in Nuclear Reactors Courtesy of New Approval
December 23, 2011, 7:09 PM
New Solar Cell Gives Its "110 Percent" in Efficiency
December 20, 2011, 6:23 PM
Military Biofuel Costs Slashed Thanks to Massive Navy Purchase
December 7, 2011, 10:32 AM
"Snowflake" Plasma Containment Field Could Hold Key to Fusion's Future
November 8, 2010, 1:30 PM
Scientist Confirm Men are More Likely to Die in "Idiotic" Ways
December 17, 2014, 1:07 PM
Shoppers Surprised to Find Cards Against Humanity's Bullsh*t is Real Feces
December 16, 2014, 11:14 PM
Air Force Worries Hot Fuel Could Harm F-35, "Proactively" Paints Trucks Shiny
December 11, 2014, 9:06 AM
McDonald's is Testing Tablet-Based Burger Customization at 30 Franchises
December 10, 2014, 11:30 AM
Detroit Pulls Together Amidst Massive Blackout
December 2, 2014, 3:57 PM
Some Dark Side For Your Black Friday: Official Star Wars Ep. VII Trailer Lands
November 28, 2014, 1:02 PM
Most Popular Articles
BlackBerry Classic Sells Out Online (Seriously, It Has) for North America
December 15, 2014, 7:07 PM
After Coming So Close to Recovering, Northern White Rhino is Nearly Extinct
December 15, 2014, 11:30 AM
Peter Sunde is Sickened by Today's Pirate Bay, Say Internet Activism is Dying
December 15, 2014, 6:02 AM
Quick Note: Windows Phone Finally Gets Candy Crush Saga
December 13, 2014, 2:03 PM
Paramount Bans Team America Screenings, Cowers Submissively to North Korea
December 18, 2014, 10:26 PM
Latest Blog Posts
Sceptre Airs 27", 120 Hz. 1080p Monitor/HDTV w/ 5 ms Response Time for $220
Dec 3, 2014, 10:32 PM
Costco Gives Employees Thanksgiving Off; Wal-Mart Leads "Black Thursday" Charge
Oct 29, 2014, 9:57 PM
"Bear Selfies" Fad Could Turn Deadly, Warn Nevada Wildlife Officials
Oct 28, 2014, 12:00 PM
The Surface Mini That Was Never Released Gets "Hands On" Treatment
Sep 26, 2014, 8:22 AM
ISIS Imposes Ban on Teaching Evolution in Iraq
Sep 17, 2014, 5:22 PM
More Blog Posts
Copyright 2014 DailyTech LLC. -
Terms, Conditions & Privacy Information