David Kirkpatrick

April 22, 2010

Quantum computing improvement

This is the first quantum computing post in a couple of months. This is a promising finding.

The release:

Bizarre matter could find use in quantum computers

Rice physicists: Odd electron mix has fault-tolerant quantum registry

IMAGE: From left, Rice physicist Rui-Rui Du, graduate students Chi Zhang and Yanhua Dai, and former postdoctoral researcher Tauno Knuuttila (not pictured) have found that odd groupings of ultracold electrons could…

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HOUSTON — (April 21, 2010) — There are enticing new findings this week in the worldwide search for materials that support fault-tolerant quantum computing. New results from Rice University and Princeton University indicate that a bizarre state of matter that acts like a particle with one-quarter electron charge also has a “quantum registry” that is immune to information loss from external perturbations.

The research appeared online April 21 in Physical Review Letters. The team of physicists found that ultracold mixes of electrons caught in magnetic traps could have the necessary properties for constructing fault-tolerant quantum computers — future computers that could be far more powerful than today’s computers. The mixes of electrons are dubbed “5/2 quantum Hall liquids” in reference to the unusual quantum properties that describe their makeup.

“The big goal, the whole driving force, besides deep academic curiosity, is to build a quantum computer out of this,” said the study’s lead author Rui-Rui Du, professor of physics at Rice. “The key for that is whether these 5/2 liquids have ‘topological’ properties that would render them immune to the sorts of quantum perturbations that could cause information degradation in a quantum computer.”

Du said the team’s results indicate the 5/2 liquids have the desired properties. In the parlance of condensed-matter physics, they are said to represent a “non-Abelian” state of matter.

Non-Abelian is a mathematical term for a system with “noncommutative” properties. In math, commutative operations, like addition, are those that have the same outcome regardless of the order in which they are carried out. So, one plus two equals three, just as two plus one equals three. In daily life, commutative and noncommutative tasks are commonplace. For example, when doing the laundry, it doesn’t matter if the detergent is added before the water or the water before the detergent, but it does matter if the clothes are washed before they’re placed in the dryer.

“It will take a while to fully understand the complete implications of our results, but it is clear that we have nailed down the evidence for ‘spin polarization,’ which is one of the two necessary conditions that must be proved to show that the 5/2 liquids are non-Abelian,” Du said. “Other research teams have been tackling the second condition, the one-quarter charge, in previous experiments.”

The importance of the noncommutative quantum properties is best understood within the context of fault-tolerant quantum computers, a fundamentally new type of computer that hasn’t been built yet.

Computers today are binary. Their electrical circuits, which can be open or closed, represent the ones and zeros in binary bits of information. In quantum computers, scientists hope to use “quantum bits,” or qubits. Unlike binary ones and zeros, the qubits can be thought of as little arrows that represent the position of a bit of quantum matter. The arrow might represent a one if it points straight up or a zero if it points straight down, but it could also represent any number in between. In physics parlance, these arrows are called quantum “states.” And for certain complex calculations, being able to represent information in many different states would present a great advantage over binary computing.

The upshot of the 5/2 liquids being non-Abelian is that they have a sort of “quantum registry,” where information doesn’t change due to external quantum perturbations.

“In a way, they have internal memory of their previous state,” Du said.

The conditions needed to create the 5/2 liquids are extreme. At Rice, Tauno Knuuttila, a former postdoctoral research scientist in Du’s group, spent several years building the “demagnetization refrigerator” needed to cool 5-millimeter squares of ultrapure semiconductors to within one-10,000th of a degree of absolute zero. It took a week for Knuuttila to simply cool the nearly one-ton instrument to the necessary temperature for the Rice experiments.

The gallium arsenide semiconductors used in the tests are the most pure on the planet. They were created by Loren Pfieiffer, Du’s longtime collaborator at Princeton and Bell Labs. Rice graduate student Chi Zhang conducted additional tests at the National High Magnetic Field Laboratory in Tallahassee, Fla., to verify that the 5/2 liquid was spin- polarized.

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Study co-authors include Zhang, Knuuttila, Pfeiffer, Princeton’s Ken West and Rice’s Yanhua Dai. The research is supported by the Department of Energy, the National Science Foundation and the Keck Foundation.

April 3, 2010

Plastic electronics may lower solar costs

Seems like a lot of news in solar cost reduction of late. In a related note, I’ve added a new link group to the sidebar — “Interesting blog topics” — and each link goes to a search for all my posts in that category. If you’re interested in solar news, that link is a great way to find everything I’ve covered in one spot.

From the link, the release:

PLASTIC ELECTRONICS COULD SLASH THE COST OF SOLAR PANELS

Posted Mar 30, 2010 By Chris Emery

A new technique developed by Princeton University engineers for producing electricity-conducting plastics could dramatically lower the cost of manufacturing solar panels.

By overcoming technical hurdles to producing plastics that are translucent, malleable and able to conduct electricity, the researchers have opened the door to broader use of the materials in a wide range of electrical devices.

With mounting concerns about global warming and energy demand, plastics could represent a low-cost alternative to indium tin oxide (ITO), an expensive conducting material currently used in solar panels, according to the researchers.

“Conductive polymers [plastics] have been around for a long time, but processing them to make something useful degraded their ability to conduct electricity,” said Yueh-Lin Loo, an associate professor of chemical engineering, who led the Princeton team. “We have figured out how to avoid this trade-off. We can shape the plastics into a useful form while maintaining high conductivity.”

A multi-institutional team reported on its new technique in a paper published online March 8 in the Proceedings of the National Academy of Sciences.

The area of research, known as “organic electronics” because plastics are carbon-based like living creatures, holds promise for producing new types of electronic devices and new ways of manufacturing existing technologies, but has been hampered by the mysterious loss of conductivity associated with moldable plastics.

“People didn’t understand what was happening,” said Loo, who co-wrote the paper. “We discovered that in making the polymers moldable, their structures are trapped in a rigid form, which prevented electrical current from traveling through them.”

Once they understood the underlying problem, Loo and her colleagues developed a way to relax the structure of the plastics by treating them with an acid after they were processed into the desired form.

Plastic transistor

Princeton researchers have developed a new way to manufacture electronic devices made of plastic, employing a process that allows the materials to be formed into useful shapes while maintaining their ability to conduct electricity. In the plastic transistor pictured here, the plastic is molded into interdigitated electrodes (orange) allowing current flow to and from the active channel (green). (Image: Loo Research Group)

Using the method, they were able to make a plastic transistor, a fundamental component of electronics that is used to amplify and switch electronic signals. They produced the electrodes of the transistor by printing the plastic onto a surface, a fast and cheap method similar to the way an ink-jet printer produces a pattern on a piece of paper.

Loo said the technique potentially could be scaled up for mass production presses akin to those used to print newspapers. “Being able to essentially paint on electronics is a big deal,” Loo said. “You could distribute the plastics in cartridges the way printer ink is sold, and you wouldn’t need exotic machines to print the patterns.”

By allowing plastic solar cells to be manufactured using low-cost printing techniques and by replacing ITO as the primary conducting material, the plastics the team developed hold potential for lowering the cost of solar panels.

Currently, the electricity generated by plastic solar cells is collected by a transparent metal conductor made of ITO. The conductor must be transparent so that sunlight can pass through it to the materials in solar cells that absorb the light energy.

A rare and pricey byproduct of mining, ITO had come under increasing demand for use in flat-screen televisions, mobile phones and other devices with display screens. “The cost of indium tin oxide is skyrocketing,” Loo said. “To bring down the costs of plastic solar cells, we need to find a replacement for ITO. Our conducting plastics allow sunlight to pass through them, making them a viable alternative.”

The researchers anticipate that the plastics also could replace expensive metals used in other electronic devices, such as flexible displays. In addition, the scientists are beginning to explore the use of the plastics in biomedical sensors that would display a certain color if a person had an infection. For instance, the plastics turn from yellow to green when exposed to nitric oxide, a chemical compound produced during ear infections in children.

If the devices could be produced at a low cost, they might be useful in developing countries that lack advanced medical facilities. “You wouldn’t need any fancy machines or lab equipment to diagnose an infection,” Loo said, “all you would need is your eyes to see the color change in the plastics.”

The co-authors of the paper were Joung Eun Yoo, who received her doctorate in chemical engineering from the University of Texas-Austin in 2009 with Loo as her adviser; Kimberly Baldwin, a high school student who spent a summer in Loo’s lab; Jacob Tarver, a Princeton chemical engineering graduate student; Enrique Gomez of Pennsylvania State University; Kwang Seok Lee and Yangming Sun of the University of Texas-Austin; Andres Garcia and Thuc-Quyen Nguyen of the University of California-Santa Barbara; and Hong Meng of DuPont Central Research and Development.

The research was supported by the National Science Foundation, the W.M. Keck Foundation and the Arnold and Mabel Beckman Foundation.

February 26, 2010

Quantum physics improving electronics and autos

Or so this news from Princeton purports.

The release:

SCIENTISTS FIND AN EQUATION FOR MATERIALS INNOVATION

Posted Feb 25, 2010By Chris Emery

Professor Emily Carter and graduate student Chen Huang developed a new way of predicting important properties of substances. The advance could speed the development of new materials and technologies. (Photo: Frank Wojciechowski)

Princeton engineers have made a breakthrough in an 80-year-old quandary in quantum physics, paving the way for the development of new materials that could make electronic devices smaller and cars more energy efficient.

By reworking a theory first proposed by physicists in the 1920s, the researchers discovered a new way to predict important characteristics of a new material before it’s been created. The new formula allows computers to model the properties of a material up to 100,000 times faster than previously possible and vastly expands the range of properties scientists can study.

“The equation scientists were using before was inefficient and consumed huge amounts of computing power, so we were limited to modeling only a few hundred atoms of a perfect material,” said Emily Carter, the engineering professor who led the project.

“But most materials aren’t perfect,” said Carter, the Arthur W. Marks ’19 Professor of Mechanical and Aerospace Engineering and Applied and Computational Mathematics. “Important properties are actually determined by the flaws, but to understand those you need to look at thousands or tens of thousands of atoms so the defects are included. Using this new equation, we’ve been able to model up to a million atoms, so we get closer to the real properties of a substance.”

By offering a panoramic view of how substances behave in the real world, the theory gives scientists a tool for developing materials that can be used for designing new technologies. Car frames made from lighter, strong metal alloys, for instance, might make vehicles more energy efficient, and smaller, faster electronic devices might be produced using nanowires with diameters tens of thousands of times smaller than that of a human hair.

Paul Madden, a chemistry professor and provost of The Queen’s College at Oxford University, who originally introduced Carter to this field of research, described the work as a “significant breakthrough” that could allow researchers to substantially expand the range of materials that can be studied in this manner. “This opens up a new class of material physics problems to realistic simulation,” he said.

The new theory traces its lineage to the Thomas-Fermi equation, a concept proposed by Llewellyn Hilleth Thomas and Nobel laureate Enrico Fermi in 1927. The equation was a simple means of relating two fundamental characteristics of atoms and molecules. They theorized that the energy electrons possess as a result of their motion — electron kinetic energy — could be calculated based how the electrons are distributed in the material. Electrons that are confined to a small region have higher kinetic energy, for instance, while those spread over a large volume have lower energy.

Understanding this relationship is important because the distribution of electrons is easier to measure, while the energy of electrons is more useful in designing materials. Knowing the electron kinetic energy helps researchers determine the structure and other properties of a material, such as how it changes shape in response to physical stress. The catch was that Thomas and Fermi’s concept was based on a theoretical gas, in which the electrons are spread evenly throughout. It could not be used to predict properties of real materials, in which electron density is less uniform.

The next major advance came in 1964, when another pair of scientists, Pierre Hohenberg and Walter Kohn, another Nobel laureate, proved that the concepts proposed by Thomas and Fermi could be applied to real materials. While they didn’t derive a final, working equation for directly relating electron kinetic energy to the distribution of electrons, Hohenberg and Kohn laid the formal groundwork that proved such an equation exists. Scientists have been searching for a working theory ever since.

Carter began working on the problem in 1996 and produced a significant advance with two postdoctoral researchers in 1999, building on Hohenberg and Kohn’s work. She has continued to whittle away at the problem since. “It would be wonderful if a perfect equation that explains all of this would just fall from the sky,” she said. “But that isn’t going to happen, so we’ve kept searching for a practical solution that helps us study materials.”

In the absence of a solution, researchers have been calculating the energy of each atom from scratch to determine the properties of a substance. The laborious method bogs down the most powerful computers if more than a few hundred atoms are being considered, severely limiting the amount of a material and type of phenomena that can be studied.

Carter knew that using the concepts introduced by Thomas and Fermi would be far more efficient, because it would avoid having to process information on the state of each and every electron.

As they worked on the problem, Carter and Chen Huang, a doctoral student in physics, concluded that the key to the puzzle was addressing a disparity observed in Carter’s earlier work. Carter and her group had developed an accurate working model for predicting the kinetic energy of electrons in simple metals. But when they tried to apply the same model to semiconductors — the conductive materials used in modern electronic devices — their predictions were no longer accurate.

“We needed to find out what we were missing that made the results so different between the semiconductors and metals,” Huang said. “Then we realized that metals and semiconductors respond differently to electrical fields. Our model was missing this.”

In the end, Huang said, the solution was a compromise. “By finding an equation that worked for these two types of materials, we found a model that works for a wide range of materials.”

Their new model, published online Jan. 26 in Physical Review B, a journal of the American Physical Society, provides a practical method for predicting the kinetic energy of electrons in semiconductors from only the electron density. The research was funded by the National Science Foundation.

Coupled with advances published last year by Carter and Linda Hung, a graduate student in applied and computational mathematics, the new model extends the range of elements and quantities of material that can be accurately simulated.

The researchers hope that by moving beyond the concepts introduced by Thomas and Fermi more than 80 years ago, their work will speed future innovations. “Before people could only look at small bits of materials and perfect crystals,” Carter said. “Now we can accurately apply quantum mechanics at scales of matter never possible before.”

February 7, 2010

Another step closer to quantum computers

Here’s the release from Friday:

Princeton scientist makes a leap in quantum computing

A major hurdle in the ambitious quest to design and construct a radically new kind of quantum computer has been finding a way to manipulate the single electrons that very likely will constitute the new machines’ processing components or “qubits.”

Princeton University’s Jason Petta has discovered how to do just that — demonstrating a method that alters the properties of a lone electron without disturbing the trillions of electrons in its immediate surroundings. The feat is essential to the development of future varieties of superfast computers with near-limitless capacities for data.

Petta, an assistant professor of physics, has fashioned a new method of trapping one or two electrons in microscopic corrals created by applying voltages to minuscule electrodes. Writing in the Feb. 5 edition of Science, he describes how electrons trapped in these corrals form “spin qubits,” quantum versions of classic computer information units known as bits. Other authors on the paper include Art Gossard and Hong Lu at the University of California-Santa Barbara.

Previous experiments used a technique in which electrons in a sample were exposed to microwave radiation. However, because it affected all the electrons uniformly, the technique could not be used to manipulate single electrons in spin qubits. It also was slow. Petta’s method not only achieves control of single electrons, but it does so extremely rapidly — in one-billionth of a second.

“If you can take a small enough object like a single electron and isolate it well enough from external perturbations, then it will behave quantum mechanically for a long period of time,” said Petta. “All we want is for the electron to just sit there and do what we tell it to do. But the outside world is sort of poking at it, and that process of the outside world poking at it causes it to lose its quantum mechanical nature.”

When the electrons in Petta’s experiment are in what he calls their quantum state, they are “coherent,” following rules that are radically different from the world seen by the naked eye. Living for fractions of a second in the realm of quantum physics before they are rattled by external forces, the electrons obey a unique set of physical laws that govern the behavior of ultra-small objects.

Scientists like Petta are working in a field known as quantum control where they are learning how to manipulate materials under the influence of quantum mechanics so they can exploit those properties to power advanced technologies like quantum computing. Quantum computers will be designed to take advantage of these characteristics to enrich their capacities in many ways.

In addition to electrical charge, electrons possess rotational properties. In the quantum world, objects can turn in ways that are at odds with common experience. The Austrian theoretical physicist Wolfgang Pauli, who won the Nobel Prize in Physics in 1945, proposed that an electron in a quantum state can assume one of two states — “spin-up” or “spin-down.” It can be imagined as behaving like a tiny bar magnet with spin-up corresponding to the north pole pointing up and spin-down corresponding to the north pole pointing down.

An electron in a quantum state can simultaneously be partially in the spin-up state and partially in the spin-down state or anywhere in between, a quantum mechanical property called “superposition of states.” A qubit based on the spin of an electron could have nearly limitless potential because it can be neither strictly on nor strictly off.

New designs could take advantage of a rich set of possibilities offered by harnessing this property to enhance computing power. In the past decade, theorists and mathematicians have designed algorithms that exploit this mysterious superposition to perform intricate calculations at speeds unmatched by supercomputers today.

Petta’s work is using electron spin to advantage.

“In the quest to build a quantum computer with electron spin qubits, nuclear spins are typically a nuisance,” said Guido Burkard, a theoretical physicist at the University of Konstanz in Germany. “Petta and coworkers demonstrate a new method that utilizes the nuclear spins for performing fast quantum operations. For solid-state quantum computing, their result is a big step forward.”

Petta’s spin qubits, which he envisions as the core of future quantum logic elements, are cooled to temperatures near absolute zero and trapped in two tiny corrals known as quantum wells on the surface of a high-purity, gallium arsenide chip. The depth of each well is controlled by varying the voltage on tiny electrodes or gates. Like a juggler tossing two balls between his hands, Petta can move the electrons from one well to the other by selectively toggling the gate voltages.

Prior to this experiment, it was not clear how experimenters could manipulate the spin of one electron without disturbing the spin of another in a closely packed space, according to Phuan Ong, the Eugene Higgins Professor of Physics at Princeton and director of the Princeton Center for Complex Materials.

Other experts agree.

“They have managed to create a very exotic transient condition, in which the spin state of a pair of electrons is in that moment entangled with an almost macroscopic degree of freedom,” said David DiVencenzo, a research staff member at the IBM Thomas J. Watson Research Center in Yorktown Heights, N.Y.

Petta’s research also is part of the fledgling field of “spintronics” in which scientists are studying how to use an electron’s spin to create new types of electronic devices. Most electrical devices today operate on the basis of another key property of the electron — its charge.

There are many more challenges to face, Petta said.

“Our approach is really to look at the building blocks of the system, to think deeply about what the limitations are and what we can do to overcome them,” Petta said. “But we are still at the level of just manipulating one or two quantum bits, and you really need hundreds to do something useful.”

As excited as he is about present progress, long-term applications are still years away. “It’s a one-day-at-a-time approach,” Petta said.

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August 6, 2009

Practical graphene

The previous post was a bit of skylarking on practical solar power, this post is right here on the ground about a current practical application for graphene. I have a feeling I’ve have the opportunity to do many more posts along these lines about the highly touted nanomaterial.

From the first link:

A startup company in Jessup, MD, hopes later this year to bring to market one of the first products based on the nanomaterial graphene. Vorbeck Materials is making conductive inks based on graphene that can be used to print RFID antennas and electrical contacts for flexible displays. The company, which is banking on the low cost of the graphene inks, has an agreement with the German chemical giant BASF and last month received $5.1 million in financing from private-investment firm Stoneham Partners.

Since it was first created in the lab in 2004, graphene has been hailed as a wonder material: the two-dimensional sheets of carbon atoms are the strongest material ever tested, and graphene’s electrical properties make it a potential replacement for silicon in faster computer chips. Synthesizing pristine graphene of the quality needed to make transistors, though, remains a painstaking process that, as yet, can’t be done on an industrial scale, though researchers are working on this problem.

Vorbeck Materials is making what company scientific advisor Ilhan Aksay calls “defective” graphene in large quantities. Though the electrical properties of the graphene aren’t good enough to support transistors, it’s still strong and conductive.

Vorbeck Materials licensed their method for making “crumpled” graphene from Aksay, a professor of chemical engineering at Princeton University. Vorbeck Materials says the inks made with this crumpled graphene are conductive and cheap enough to compete with silver and carbon inks currently used in displays and RFID-tag antennas. (Another startup working on defective graphene, Graphene Energy of Austin, TX, is using a similar form of the material to make electrodes for ultracapacitors.)

Crumpled graphene: Conductive inks made by startup company Vorbeck Materials contain crumpled graphene. This atomic-force microscope image is colorized to show the topography of a piece of graphene of the type used in the inks; red areas are higher and blue are lower. Credit: Ilhan Aksay and Hannes Schniepp

Crumpled graphene: Conductive inks made by startup company Vorbeck Materials contain crumpled graphene. This atomic-force microscope image is colorized to show the topography of a piece of graphene of the type used in the inks; red areas are higher and blue are lower. Credit: Ilhan Aksay and Hannes Schniepp

July 8, 2009

No carbon plan at G-8 summit

Not really surprising given the global recession, among many other issues around climate change politics.

From the link:

The failure to establish specific targets on climate change underscored the difficulty in bridging longstanding divisions between the most developed countries like the United States and developing nations like China and India. In the end, people close to the talks said, the emerging powers refused to agree to the specific emissions limits because they wanted industrial countries to commit to midterm goals in 2020, and to follow through on promises of financial and technological help.

“They’re saying, ‘We just don’t trust you guys,’ ” said Alden Meyer of the Union of Concerned Scientists, an advocacy group based in the United States. “It’s the same gridlock we had last year when Bush was president.”

American officials said they still had made an important breakthrough because the G-8 countries within the negotiations agreed to adopt the 2050 reduction goals, even though the developing countries would not.

Of course if these guys would just listen to this carbon emmission plan out of Princeton University the world could be saved, or something like that.

(Head below the fold for the full Princeton release.) (more…)

October 22, 2008

Moving toward quantum computing

Making headway, it seems. This is amazing — storing information inside the nucleus of an atom!

From the link:

The problem: How do you isolate a quantum bit from a noisy environment to protect the deli-cate quantum information, while at the same time allowing it to interact with the outside world so that it can be manipulated and measured?

The team, with scientists and engineers from Oxford and Princeton universities and Lawrence Berkeley National Laboratory, reported a solution to this problem in the Oct. 23 issue of the journal Nature.

The team’s plan was to devise a hybrid system using both the electron and nucleus of an atom of phosphorous embedded in a silicon crystal. Each behaves as a tiny quantum magnet capa-ble of storing quantum information, but inside the crystal the electron is more than a million times bigger than the nucleus, with a magnetic field that is a thousand times stronger. This makes the electron well-suited for manipulation and measurement, but not so good for storing information, which can become rapidly corrupted. This is where the nucleus comes in: when the information in the electron is ready for storage, it is moved into the nucleus where it can survive for much longer times.

Go below the fold for a release from October 23 on this story.

(more…)

July 15, 2008

The latest in energy-efficient lighting

I love the idea of energy-efficient lighting. Went all compact fluorescent a couple of years ago, and haven’t looked back. I’m pretty excited about the possibilities of LED once that tech comes way, way down in price.

(Update 7/28/08 — This update is positioned this high because I wanted to get it above long release. Here’s a link to a Technology Review article on this release’s material.)

On the same vein, here’s a press release from the University of Michigan News Service on the latest technology in efficient lighting:

July 15, 2008

Freeing light shines promise on energy-efficient lighting

ANN ARBOR, Mich.—The latest bright idea in energy-efficient lighting for homes and offices uses big science in nano-small packages to dim the future Edison’s light bulb.

In the August issue of Nature Photonics, available online, scientists at the University of Michigan and Princeton University announce a discovery that pushes more appealing white light from organic light-emitting devices.

More white light is the holy grail of the next generation of lighting. The innovation in the paper “Enhanced Light Out-Coupling of Organic Light-Emitting Devices Using Embedded Low-Index Grids” describes a way to deliver significantly more bright light from a watt than incandescent bulbs.

“Our demonstration here shows that OLEDs are a very exciting technology for use in interior illumination,” said Stephen Forrest, U-M professor of electrical engineering and physics and vice president for research. “We hope that white emitting OLEDs will play a major role in the world of energy conservation.”

Forrest and co-author Yuri Sun, visiting U-M from Princeton University, have wrestled with a classic problem in the new generation of lighting called white organic light-emitting devices, or WOLED: Freeing the light generated, but mostly trapped, inside the device.

A lighting primer: Incandescent light bulbs give off light as a by-product of heat, The light is appealing, but inefficient, putting out 15 lumens of light for every watt or electricity.

The best fluorescent tube lights put out some 90 lumens of light per watt, but the light can be harsh, the fixtures are expensive, and the tubes lose their efficiency with age. And they rely on many environmentally unfriendly substances such as mercury.

WOLEDs show promise of providing a light that’s much easier to manipulate, while being long lasting and able to provide in different shapes, from panels to bulbs and more. WOLEDs generate white light by using electricity to send an electron into nanometer thick layers of organic materials that serve as semiconductors. These carbon-based materials are dyes, the ones used in photographic prints and car paint, so they are very inexpensive, and can be put on plastic sheets or metal foils, further reducing costs.

The excited electron in these layers casts bright white light. The bad news, Forrest said, has been that some 60 percent of it is trapped inside the layers, much the way light under water reflects back into the pool, making the water surface seem like a mirror when viewed from underneath.

The Nature Photonics paper describes a tandem system of organic grids and micro lenses that guide the light out of the thin layers and into the air. The grids refract the trapped light, bouncing it into a layer of dome-shaped lenses that then pull the light out.

This process—all of which is packed into a lighting sandwich roughly the thickness of a sheet of paper—was shown to emit approximately 70 lumens from a single watt of power.

More light out means getting more bang for the electricity buck, a crucial question since 22 percent of the U.S. electricity consumption is lighting.

“If you can change the light efficiency by just a few percentage points, there’s a few less coal plants you’ll need,” Forrest said.

Reducing the amount of coal-generated electricity and finding more efficient ways to power appliances and lighting is one of the focuses of U-M’s Michigan Memorial Phoenix Energy Institute, and the WOLED work is one example of how science can open new doors in conservation, said Gary Was, institute director.

“That energy efficient lighting can be made from the same materials as car paint and that they can be made in such thin, formable sheets boggles the mind,” Was said. “This is one of many exciting creations that research is giving us in the pursuit of energy efficiency. This is also the kind of innovation that is required in the drive for energy sustainability.

Forrest said WOLED work isn’t done yet. The fun part, he said, is that WOLEDs can be framed in different forms.

“Plugging into a wall at low voltage, putting it on a flexible metal foil, or on plastic that won’t break when you drop it,” Forrest said. “This is what makes it so fun because it’s such a unique lighting source.”

The research was funded by the U.S. Department of Energy through a subcontract from the University of Southern California and by Universal Display Corp.

Forrest is part of the Michigan Memorial Phoenix Energy Institute, which develops, coordinates and promotes multidisciplinary energy research and education at U-M. He also is on the scientific advisory board of Universal Display Corp.

The next challenge, he said, is to reduce the cost, which currently is too high to be commercially competitive.

“You have to be able to do this dirt cheap, Forrest said. “People don’t spend much for their light bulbs.”

 

 

Related Links:

Michigan Memorial Phoenix Energy Institute