David Kirkpatrick

September 2, 2010

Improvements in LED lighting coming?

Looks pretty promising. I haven’t blogged about alternative lighting in a while, but I remain very fascinated about the potential for LED lighting. I have two LED bulbs right now, and as cool as they are (figuratively and literally) they suffer from the main complaints against LEDs right now — they are quite dim (albeitly by design in these particular bulb’s case) and they are very unidirectional and suitable only for spot lighting applications.

Here’s the latest news in LEDs and looks to be quite ambitious and very interesting. I’m looking forward to being able to replace all my residential lighting with crazy long-lasting and cheap-to-run LEDs.

From the link:

Researchers from the Nichia Corporation in Tokushima, Japan, have set an ambitious goal: to develop a white LED that can replace every interior and exterior light bulb currently used in homes and offices. The properties of their latest white LED – a luminous flux of 1913 lumens and a luminous efficacy of 135 lumens per watt at 1 amp – enable it to emit more light than a typical 20-watt fluorescent bulb, as well as more light for a given amount of power. With these improvements, the researchers say that the new LED can replace traditional fluorescent bulbs for all general lighting applications, and also be used for automobile headlights and LCD backlighting.

The history of luminous efficacy in different types of lighting shows the rapid improvements in white LEDs. The years in which the white light sources were developed are also shown. Credit: Yukio Narukawa, et al.

August 21, 2009

New process lowers cost of LEDs

A lot of work has been done in the world of LEDs as a viable, cost-effective lighting source — particularly with OLEDs — and here’s some interesting news on inorganic LEDs and a new technique to help bring manufacuturing costs down for that lighting tech.

From the second link:

A new technique makes it possible to print flexible arrays of thin inorganic light-emitting diodes for displays and lighting. The new printing process is a hybrid between the methods currently used to make inorganic and organic LEDs, and it brings some of the advantages of each, combining the flexibility, thinness and ease of manufacturing organic polymers with the brightness and long-term stability of inorganic compounds. It could be used to make high-quality flexible displays and less expensive LED lighting systems.

Inorganic LEDs are bright and long lasting, but the expense of manufacturing them has led to them being used mainly in niche applications such as billboard-size displays for sports arenas. What’s more, the manufacturing process for making inorganic LED displays is complex, because each LED must be individually cut and placed, says John Rogers, a materials science professor in the Beckman Institute at the University of Illinois at Urbana-Champaign. So display manufacturers have turned to organic materials, which can be printed and are cheaper. While LED-based lighting systems are attractive because of their low energy consumption, they remain expensive. The new printing process, developed by Rogers and described today in the journal Science, could bring down the cost of inorganic LEDs because it would require less material and simpler manufacturing techniques.

July 23, 2009

OLEDs hit the market …

Filed under: Business, Science, Technology — Tags: , , , , — David Kirkpatrick @ 4:37 pm

… at $100 per square inch for prototypes. Ouch.

From the link:

Someday, our ceilings and walls might radiate light, illuminating indoor spaces as brightly and evenly as natural daylight.

Though that possibility remains years off, the Dutch electronics company Philips is letting people tinker with the technology that would enable it.

The world’s biggest lighting maker has begun selling do-it-yourself kits with little glowing wafers called “Lumiblades.” They come in red, white, blue or green for anyone who wants to pay nearly $100 per square inch.

It’s one of the first chances people outside research labs have had to get their hands on lights made from organic light emitting diodes, or OLEDs.

The company’s aim is to get designers, architects and other creative types thinking about how these flat lights can be used, and to start collaborating on early products.

Head here for more blog posts on OLEDs.

June 18, 2009

Cheaper OLEDs

I haven’t had an opportunity to blog about OLEDs in a while, but this looks like a real cost breakthrough. OLEDs have the potential to revolutionize lighting and display technology.

From the link:

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.

April 7, 2009

The latest in LEDs

It’s been far, far too long since I’ve had a reason to blog about LED lighting. I’ve been champing at the bit for this tech to become a viable option for home lighting. Right now the actual products just aren’t quite there, and they are very expensive for the most part.

I received two 40 watt equivalent LED spots from an enthusiast friend at the holidays. They aren’t ideal, but I’m damned excited to have them burning daily. Cool to the touch, even with 24 hour a day use, and throwing off a bluish, broad spectrum of light. Someday soon these things will be ready for prime time.

Here’s the latest in LED research news:

Cheap and efficient white light LEDs new design described in AIP’s Journal of Applied Physics

IMAGE: Light produced by a new type of light emitting diode (LED) made from inexpensive, plastic-like organic materials.

Click here for more information. 

COLLEGE PARK, MD, April 7, 2009 — Roughly 20 percent of the electricity consumed worldwide is used to light homes, businesses, and other private and public spaces. Though this consumption represents a large drain on resources, it also presents a tremendous opportunity for savings. Improving the efficiency of commercially available light bulbs — even a little — could translate into dramatically lower energy usage if implemented widely.

In the latest issue of Journal of Applied Physics, published by the American Institute of Physics (AIP), a group of scientists at the Chinese Academy of Sciences is reporting an important step towards that goal with their development of a new type of light emitting diode (LED) made from inexpensive, plastic like organic materials. Designed with a simplified “tandem” structure, it can produce twice as much light as a normal LED — including the white light desired for home and office lighting.

“This work is important because it is the realization of rather high efficiency white emission by a tandem structure,” says Dongge Ma , who led the research with his colleagues at the Changchun Institute of Applied Chemistry at the Chinese Academy of Sciences.

Found in everything from brake lights to computer displays, LEDs are more environmentally friendly and much more efficient than other types of light bulbs. Incandescent bulbs produce light by sending electricity through a thin metal filament that glows red hot. Only about five percent of the energy is turned into light, however. The rest is wasted as heat. Compact fluorescent bulbs, which send electricity through a gas inside a tube, tend to do much better. They typically turn 20 percent or more of the electricity pumped through them into light. But compact fluorescents also contain small amounts of mercury vapor, an environmental toxin.

LEDs on the other hand, are made from thin wafers of material flanked by electrodes. When an electric current is sent through the wafers, it liberates electrons from the atoms therein, leaving behind vacancies or “holes.” When some of the wandering electrons and holes recombine, they create a parcel of light, or photon. These photons emerge from the side of the wafer as visible light. This turns 20 to 50 percent, or even more, of the input energy into light. LEDs also concentrate a lot of light in a small space.

Producing LEDs that can compete with traditional light bulbs for cost and efficiency is one thing. Making LEDs that consumers want to use to light their homes is quite another. One of the main barriers to the widespread use of LED lights is the light itself. LEDs can easily be manufactured to produce light of a single color — like red — with applications such as traffic lights and auto brake lights. Indoor lighting though, requires “natural” white light. This quality is measured by the color-rendering index (CRI), which assigns a value based on the light source’s ability to reproduce the true color of the object being lit. For reading light, a CRI value of 70 or more is optimal. LEDs can produce white light by combining a mixture of blue, green, and red light, or by sending colored light through a filter or a thin layer of phosphors — chemicals that glow with several colors when excited. However, these solutions increase costs. To reach a larger market, scientists would like to make inexpensive LEDs that can produce white light on their own.

The authors of this paper report important advances towards this goal. First, they built LEDs from organic, carbon-based materials, like plastic, rather than from more expensive semiconducting materials such as gallium, which also require more complicated manufacturing processes. Second, they demonstrated, for the first time, an organic white-light LED operating within only a single active layer, rather than several sophisticated layers. Moreover, by putting two of these single-layer LEDs together in a tandem unit, even higher efficiency is achieved. The authors report that their LED was able to achieve a CRI rating of nearly 70 — almost good enough to read by. Progress in this area promises further reduction in the price of organic LEDs.

 

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The work of Dongge Ma and colleagues was funded by the Hundreds Talents program of Chinese Academy of Sciences, the National Science Fund for Distinguished Young Scholars of China, the Foundation of Jilin Research Council, Foundation of Changchun Research Council, Science Fund for Creative Research Groups of NSFC, and the Ministry of Science and Technology of China.

The article “A high-performance tandem white organic LED combining highly effective white units and their interconnection layer” by Qi Wang et al. was published online on April 6, 2009 [J. Appl. Phys. 105, 076101 (2009)]. The article is available at http://link.aip.org/link/?JAPIAU/105/076101/1.

ABOUT THE JOURNAL

Journal of Applied Physics, published by the American Institute of Physics (AIP), is an archival journal presenting significant new results in applied physics. The journal publishes original and review articles that emphasize understanding of the physics underlying modern technology. See: http://jap.aip.org/.

ABOUT AIP

The American Institute of Physics (AIP) is a not-for-profit membership corporation chartered in 1931 for the purpose of advancement and diffusion of the knowledge of physics and its application to human welfare. An umbrella organization for 10 Member Societies, AIP represents over 134,000 scientists, engineers and educators and is one of the world’s largest publishers of physics journals. A total-solution provider of publishing services, AIP also publishes 12 journals of its own (many of which have the highest impact factors in their category), two magazines, and the AIP Conference Proceedings series. Its online publishing platform Scitation (registered trademark) hosts more than 1,000,000 articles from more than 175 scholarly journals, as well as conference proceedings, and other publications of 25 learned society publishers. See: http://www.aip.org.

October 11, 2008

Flexible OLED offers new lighting options

Filed under: Business, Science, Technology — Tags: , , , , , , — David Kirkpatrick @ 1:28 pm

I’ve done a fair amount of blogging on OLEDs (hit this link for those posts and all my praise for the tech) so I do follow the developments and breakthroughs to a great extent. This application of Organic Light-Emitting Diodes is very exciting because it has the possibility of completely revolutionizing the concept of artificial lighting.

Plus it’s just plain cool.

From the second link:

On a bank of the Mohawk River, a windowless industrial building of corrugated steel hides something that could make floor lamps, bedside lamps, wall sconces and nearly every other household lamp obsolete. It’s a machine that prints lights.

The size of a semitrailer, it coats an 8-inch wide plastic film with chemicals, then seals them with a layer of metal foil. Apply electric current to the resulting sheet, and it lights up with a blue-white glow.

You could tack that sheet to a wall, wrap it around a pillar or even take a translucent version and tape it to your windows. Unlike practically every other source of lighting, you wouldn’t need a lamp or conventional fixture for these sheets, though you would need to plug them into an outlet.

The sheets owe their luminance to compounds known as organic light-emitting diodes, or OLEDs. While there are plenty of problems to be worked out with the technology, it’s not the dream of a wild-eyed startup.

OLEDs are beginning to be used in TVs and cell-phone displays, and big names like Siemens and Philips are throwing their weight behind the technology to make it a lighting source as well. The OLED printer was made by General Electric Co. on its sprawling research campus here in upstate New York. It’s not far from where a GE physicist figured out a practical way to use tungsten metal as the filament in a regular light bulb. That’s still used today, nearly a century later.