TreeHugger has a post on using graphene for energy efficient lighting - Move Over OLEDs: Scientists Create Cheap, Fully Recyclable Lighting Material.

Swedish and American researchers have just developed a fully recyclable lighting component with what Science Daily is terms a "new super material": graphene. Graphene is both inexpensive to produce and is 100% recyclable, and could be used to create glowing wallpaper made out of plastic--much like )LEDs could. But graphene appears to improve on OLEDs in some very big ways . . .

As you know, we've been big fans of the very efficient, long-lasting Light Emitting Diodes and Organic LED technology. But as Science Daily notes, there are still problems:

Today's OLEDs have two drawbacks -- they are relatively expensive to produce, and the transparent electrode consists of the metal alloy indium tin oxide. The latter presents a problem because indium is both rare and expensive and moreover is complicated to recycle.

Researchers believe they've found a solution by creating an organic light-emitting electrochemical cell (LEC) with the transparent electrode made of the "carbon material graphene." Graphene is used instead of conventional metal electrodes--and since everything in an LEC, including the graphene, can be created from liquid solutions, they will be able to be produced through a printing process. This makes them much more efficient--and much less expensive--to create en masse than OLEDs. Researchers involved in the project say that graphene paves the way for cheap production of plastic-based lighting, perhaps for the first time.

Technology Review has an update on quantum dot OLED technology - A Cheap Route to Robust LEDs.

Organic light-emitting diodes (OLEDs) are steadily making their way into commercial devices like cell phones and flat-screen displays. They're fabricated with layers of organic polymers, which make them flexible, and they use less power and less expensive materials than liquid crystal displays.

The downside is that because the polymers react easily with oxygen and water, OLEDs are expensive to produce--they have to be created in high-vacuum chambers--and they need extra protective packaging layers to make sure that once they're integrated into display devices, they don't degrade when exposed to air or moisture.

MIT chemical-engineering professor Karen Gleason and MIT postdoc Sreeram Vaddiraju have developed a process that aims to solve the problems of high fabrication costs and instability for OLEDs while still maintaining their flexibility. Gleason's solution is a hybrid light-emitting diode, or HLED. The device would incorporate both organic and inorganic layers, combining the flexibility of an OLED with the stability of an inorganic light-emitting material. "The idea is to have a mixed bag and capture the qualities that allow inexpensive fabrication and stability," Gleason says.

Gleason starts with a substrate of electrically conducting organic polymer, which she creates through a chemical vapor deposition process in a low-vacuum chamber. It's the only step in the process that requires a vacuum, which should make the approach cheaper than conventional methods. For the light-emitting layer, Gleason uses quantum dots, nanocrystals of inorganic semiconductors; each quantum dot can be "tuned" to emit certain frequencies of light. Although quantum dots are inflexible themselves, they're so small--two to six nanometers across--that even arranging them side by side in a continuous film still allows for flex in the material.

Technology Review has an update on cheap, energy efficient OLED lighting - Ultra-Efficient Organic LEDs.

An organic light-emitting diode (OLED) developed in Germany has the potential to produce the same quality of white light as incandescent bulbs but with power efficiencies considerably better than even fluorescent lighting.

The prototype OLED could emerge as an ultra-efficient light source for displays and general lighting, says Sebastian Reineke, who led the research at the Institute for Applied Photophysics, in Dresden, Germany. The long-term goal is to fabricate the device using conventional low-cost roll-to-roll printing.

In recent years, many countries have begun looking to switch from incandescent lighting to compact fluorescent bulbs because the latter are so much more energy efficient. There has also been a lot of interest in using light-emitting diodes (LEDs) for displays and general lighting, again because of the potential energy savings they offer.

But with both fluorescent and LED lighting, the quality of white light produced has always left something to be desired. Fluorescent lighting can make people appear unhealthy because less red light is emitted, while most white LEDs on the market today have a bluish quality, making them appear cold.

In contrast, OLEDs can be made from a wide range of materials, so achieving good-quality white light is less challenging, says Reineke. It has not been the quality of light that has let OLEDs down but rather their efficiencies. Fluorescent lighting typically operates at around 60 to 70 lumens per watt, while incandescent bulbs operate at about 10 to 17 lumens per watt. In contrast, says Reineke, the best reported power efficiency of an OLED until now was 44 lumens per watt.

In this week's issue of the journal Nature, Reineke and his colleagues report a novel structural design for an OLED that exhibits efficiencies of 90 lumens per watt and shows potential to go up to 124 lumens per watt.

"These efficiencies are very compelling," says Peter Kazlas, director of device development for QD Vision, a company based in Cambridge, MA, that's developing quantum-dot-based LED lighting.

"OLEDs have the potential to grow into a really very energy-efficient light source," adds Kristin Knappstein, business-development manager at Philips Lighting, in Aachen, Germany. Her company already has an OLED lighting product on the market called Lumiblade. "In production, we achieve levels of between 15 and 20 lumens per watt," she says, adding that the ultimate potential is for the technology to reach efficiencies as high as 150 lumens per watt.

Seth Coe-Sullivan flicks the switches on two desk lamps, and even from across the conference room, it's immediately obvious which light the chief technology officer of QD Vision is there to brag about. The light coming from the lamp on the left is a harsh bluish white. The lamp on the right casts a warmer, more yellow glow. Coe-Sullivan holds a hand under each lamp. The hand under the bluish light looks pale and sickly; the other looks darker and healthier. The harsher light lacks wavelengths in the red end of the spectrum, so there's no light to illuminate the reddish tinge that blood provides to human skin.

QD Vision, based in Watertown, MA, is promoting a new LED-based lamp that it made with Nexxus Lighting of Charlotte, NC. Nexxus makes a lamp designed to screw into standard sockets used in recessed ceiling lighting. It consists of an array of white-light LEDs encircled by fins that remove excess heat. QD Vision adds an optic--a plastic cover with a special coating that snaps into place over the LEDs.

It's that coating that makes the difference in the quality of the light. It consists of quantum dots--tiny bits of semiconductor material just a few nanometers in diameter. When excited by a light source--in this case, the LEDs--quantum dots radiate light in a wavelength that varies according to the size of the dot: a two-nanometer dot gives off blue light, a four-nanometer dot emits green, and a six-nanometer dot produces red. The company makes the dots in controlled sizes, then mixes them in the right ratio to get the desired color.

This color-tailoring ability solves one of the major problems with using LEDs for general lighting applications. LEDs are appealing because they last for years, use perhaps 20 percent of the electricity of a standard incandescent bulb, and are highly efficient at converting electricity into visible light instead of into heat. But to make white light, you either have to mix together LEDs of different colors or use a blue LED coated with a phosphor that emits yellow light to produce a whitish mix. The problem with the phosphors is that they don't emit evenly across the visible spectrum. They tend to have gaps in the green section and even more so in the red, leading to the harsher, bluish light. "You can't precisely tailor phosphors anywhere in the visible spectrum," says Dan Button, QD Vision's CEO.

Technology Review reports that researchers have found a way to boost the light emitted from OLEDs (the future of energy efficient lighting) - More-Efficient OLED Lighting.

Energy efficiency and flexible lighting applications have long been the promise of organic light emitting diodes (OLEDs). The technology hasn't lived up to its promise, however, because in typical OLEDs, only 20 percent of the light generated is released from the device. That means that most light is trapped inside the bulb, making it highly inefficient.

Researchers at the University of Michigan and Princeton University believe that they're on to a way to break the OLED-efficiency logjam. The scientists have designed an OLED that boosts illumination by 60 percent using a combination of an organic grid working in tandem with small micro lenses that guide the trapped light out of the device.

Stephen Forrest, a professor of electrical engineering and physics at Michigan, and Yuri Sun, from Princeton University, described the work in the August issue of Nature Photonics.

In OLEDs, white light is generated by using electricity to send an electron into nanometer-thick layers of organic materials that behave like semiconductor materials. Typically, the light in the substrate is internally reflected and runs parallel and not perpendicular. That's the crux of the problem because the light can't escape in the vertical direction without some coaxing. In Forrest's devices, the grids refract the trapped light, sending it to the five micrometers dome-shaped micro lenses. The light is sent off in a vertical orientation that helps release the trapped rays.

Forrest and his coworkers report that the technology emits about 70 lumens from a watt of power. In comparison, incandescent lightbulbs emit 15 lumens per watt. Fluorescent lights put out roughly 90 lumens of light per watt but have liabilities: they produce harsh light, lack longevity, and use environment-damaging substances like mercury.

Forrest says that the next step in the research is to use OLEDs that are more efficient than those the team used in the current project. Looking beyond the research lab work on these OLEDs, he is cautiously optimistic that it should be possible to scale up the manufacturing of the devices, and that production costs for manufacturing the new OLEDs will be competitive.

Today, an estimated 22 percent of the electricity produced goes to lighting buildings. A highly efficient form of OLED lighting could significantly reduce the electricity demand and boost savings. Another factor influencing broad adoption of LEDs is the fact that they outlast incandescent bulbs. Over the next 20 years, the rapid adoption of LED lighting in the United States could reduce electricity demands by 62 percent and thus eliminate 258 million metric tons of carbon emissions, according to the Department of Energy.