World's most efficient flexible organic light-emitting diodes created on plastic

ScienceDaily (Oct. 31, 2011) — Researchers in the University of Toronto's Department of Materials Science & Engineering have developed the world's most efficient organic light-emitting diodes (OLEDs) on plastic. This result enables a flexible form factor, not to mention a less costly, alternative to traditional OLED manufacturing, which currently relies on rigid glass.

The results are reported online in the latest issue of Nature Photonics.

OLEDs provide high-contrast and low-energy displays that are rapidly becoming the dominant technology for advanced electronic screens. They are already used in some cell phone and other smaller-scale applications.

Current state-of-the-art OLEDs are produced using heavy-metal doped glass in order to achieve high efficiency and brightness, which makes them expensive to manufacture, heavy, rigid and fragile.

"For years, the biggest excitement behind OLED technologies has been the potential to effectively produce them on flexible plastic," says Materials Science & Engineering Professor Zheng-Hong Lu, the Canada Research Chair (Tier I) in Organic Optoelectronics.

Using plastic can substantially reduce the cost of production, while providing designers with a more durable and flexible material to use in their products.

The research, which was supervised by Professor Lu and led by PhD Candidates Zhibin Wang and Michael G. Helander, demonstrated the first high-efficiency OLED on plastic. The performance of their device is comparable with the best glass-based OLEDs, while providing the benefits offered by using plastic.

"This discovery, unlocks the full potential of OLEDs, leading the way to energy-efficient, flexible and impact-resistant displays," says Professor Lu.

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The above story is reprinted from materials provided by University of Toronto Faculty of Applied Science & Engineering.

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Journal Reference:

Z. B. Wang, M. G. Helander, J. Qiu, D. P. Puzzo, M. T. Greiner, Z. M. Hudson, S. Wang, Z. W. Liu, Z. H. Lu. Unlocking the full potential of organic light-emitting diodes on flexible plastic. Nature Photonics, 2011; DOI: 10.1038/nphoton.2011.259

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Highly efficient oxygen catalyst found: Rechargeable batteries and hydrogen-fuel production could benefit

ScienceDaily (Oct. 28, 2011) — A team of researchers at MIT has found one of the most effective catalysts ever discovered for splitting oxygen atoms from water molecules -- a key reaction for advanced energy-storage systems, including electrolyzers, to produce hydrogen fuel and rechargeable batteries. This new catalyst liberates oxygen at more than 10 times the rate of the best previously known catalyst of its type.

The new compound, composed of cobalt, iron and oxygen with other metals, splits oxygen from water (called the Oxygen Evolution Reaction, or OER) at a rate at least an order of magnitude higher than the compound currently considered the gold standard for such reactions, the team says. The compound's high level of activity was predicted from a systematic experimental study that looked at the catalytic activity of 10 known compounds.

The team, which includes materials science and engineering graduate student Jin Suntivich, mechanical engineering graduate student Kevin J. May and professor Yang Shao-Horn, published their results in Science on Oct. 28.

The scientists found that reactivity depended on a specific characteristic: the configuration of the outermost electron of transition metal ions. They were able to use this information to predict the high reactivity of the new compound -- which they then confirmed in lab tests.

"We not only identified a fundamental principle" that governs the OER activity of different compounds, "but also we actually found this new compound" based on that principle, says Shao-Horn, the Gail E. Kendall (1978) Associate Professor of Mechanical Engineering and Materials Science and Engineering.

Many other groups have been searching for more efficient catalysts to speed the splitting of water into hydrogen and oxygen. This reaction is key to the production of hydrogen as a fuel to be used in cars; the operation of some rechargeable batteries, including zinc-air batteries; and to generate electricity in devices called fuel cells. Two catalysts are needed for such a reaction -- one that liberates the hydrogen atoms, and another for the oxygen atoms -- but the oxygen reaction has been the limiting factor in such systems.

Other groups, including one led by MIT's Daniel Nocera, have focused on similar catalysts that can operate -- in a so-called "artificial leaf" -- at low cost in ordinary water. But such reactions can occur with higher efficiency in alkaline solutions, which are required for the best previously known catalyst, iridium oxide, as well as for this new compound.

Shao-Horn and her collaborators are now working with Nocera, integrating their catalyst with his artificial leaf to produce a self-contained system to generate hydrogen and oxygen when placed in an alkaline solution. They will also be exploring different configurations of the catalyst material to better understand the mechanisms involved. Their initial tests used a powder form of the catalyst; now they plan to try thin films to better understand the reactions.

In addition, even though they have already found the highest rate of activity yet seen, they plan to continue searching for even more efficient catalyst materials. "It's our belief that there may be others with even higher activity," Shao-Horn says.

Jens Norskov, a professor of chemical engineering at Stanford University and director of the Suncat Center for Interface Science and Catalysis there, who was not involved in this work, says, "I find this an extremely interesting 'rational design' approach to finding new catalysts for a very important and demanding problem."

The research, which was done in collaboration with visiting professor Hubert A. Gasteiger (currently a professor at the Technische Universität München in Germany) and professor John B. Goodenough from the University of Texas at Austin, was supported by the U.S. Department of Energy's Hydrogen Initiative, the National Science Foundation, the Toyota Motor Corporation and the Chesonis Foundation.

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The above story is reprinted from materials provided by Massachusetts Institute of Technology. The original article was written by David L. Chandler, MIT News Office.

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Journal Reference:

J. Suntivich, K. J. May, H. A. Gasteiger, J. B. Goodenough, Y. Shao-Horn. A Perovskite Oxide Optimized for Oxygen Evolution Catalysis from Molecular Orbital Principles. Science, 2011; DOI: 10.1126/science.1212858

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Intel to Mass-Produce New 3-D Transistors for Faster, More Efficient Computer Chips

3-D Transistor This image shows the vertical fins of Intel’s 22 nanometer microprocessor using 3-D Tri-Gate transistors. Intel
In a move that could remake the microchip industry, Intel announced Wednesday it will start mass-producing the first three-dimensional silicon transistors. The 3-D transistor design, which Intel says will improve efficiency by more than one-third, will be integrated into a 22-nanometer node in an Intel chip called Ivy Bridge.
It’s a major change from the two-dimensional flat transistor structure we all know and love, which has powered every computer chip for the last 50 years. The 3-D switch design and the scale of its production will allow Moore’s Law to advance apace, Intel said.
Moore’s Law holds that the number of transistors that can be placed on a circuit will double every two years, but this places limits on the circuits’ size — a growing problem as engineers cram greater numbers of transistors onto ever-tinier chips. A 3-D switch could allow computer chips to be built like skyscrapers, optimizing space by building upward, and thereby allowing uninhibited transistor growth.
The Tri-Gate transistors consist of a thin 3-D silicon fin that arises vertically from the silicon substrate, Intel explains. Each fin has three gates, one on the top and one on each side, which allows for greater transistor current control. When it’s on, current flow is more efficient, and when the switches are off, the flow of electrons is closer to zero. By contrast, flat transistors have one gate, only on top.
All this leads to greater efficiency, allowing chips to operate at a lower voltage and with lower leakage — Intel claims a whopping 37 percent performance increase over its 2-D chips. Since the fins and their gates are vertical, more transistors can be packed close together. Eventually, designers will be able to make taller fins, aiming for even better performance.
“It will give product designers the flexibility to make current devices smarter and wholly new ones possible,” said Mark Bohr, a senior fellow at Intel.
More than 6 million 22-nm Tri-Gate transistors could fit inside the period at the end of this sentence, according to the company. (If you zoom in, who knows how many could fit!)
The new transistors will be integrated into Ivy Bridge-based Intel Core processors by the end of this year, which consumers will be able to get in 2012, Intel said.
Plenty of other chip designers have been talking about 3-D chips — just last month, we saw a 2-D reprogrammable one designed to behave as if it was a 3-D one. But Intel has taken it a step further by figuring out how to mass-produce them.
It’s technically 3-D because the switches are vertical and horizontal, but the transistors are not stacked, allowing electrons to flow in three dimensions — that’s a holy Grail of microprocessor design. But a new circuit design that allows more transistors on tinier spaces certainly sounds like a major breakthrough.
[IBM via PC Magazine]

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