I have written a couple of posts in the past about innovations in lighting. In a post entitled LED to the Future, for example, I discussed how light emitting diodes (or LEDs) are being touted as the future of the lighting industry because of the energy they can save. LEDs, however, remain almost prohibitively expensive for household use. In a blog entitled A Post on the Light Side, I discussed how some new approaches are extending the life of incandescent light bulbs. Another new approach to lighting has appeared that uses “quantum dots” [“A Quantum Leap for Lighting,” by Reena Jana, Bloomberg BusinessWeek, 1 September 2009, and “A quantum leap for lighting,” The Economist, 4 March 2010]. Jana reports:

“Compact fluorescent lights are leading the race to replace the incandescent bulb. But while efficient, CFL light can be harsh. Ditto for light-emitting diodes, or LEDs, which use even less power but are more costly. QD Vision, a Watertown (Mass.) startup, says it can lower energy use and improve light quality by combining LEDs with tiny synthetic crystals they call quantum dots. Measuring just 5 billionths of a meter wide, the crystals glow when excited by a trickle of electricity. QD Vision and its partner, Nexxus Lighting, are coming out with a $100 bulb that uses 12 watts, matches the output of a 75-watt incandescent bulb and can last 50 times longer. The device is aimed at retailers who want to cut their energy use and lower the labor costs of replacing bulbs. With funds from the U.S. Energy Dept. and the U.S. Army, QD Vision is also developing flexible light sources and large displays made with its quantum dots.”

At $100/bulb, I doubt that you’ll be seeing quantum dot bulbs installed in large numbers of households (or many businesses) anytime in the near future. Although the long-term savings look good, the short-term investment could be quite off-putting. I’m always skeptical of claims about how long bulbs will last. My experience with CFL bulbs is that they don’t last anywhere near the five-year life span manufacturers claim for them. Still, quantum dot bulbs are getting some pretty good PR. The Economist article reports:

“How many inventions does it take to change a light bulb? More than you might think. Around the world, many people are switching from traditional incandescent bulbs to compact fluorescent (CFL) bulbs, which require less energy to produce a given amount of light, and therefore save money and reduce carbon emissions. But CFLs themselves may soon be overhauled by light emitting diodes (LEDs), which are even more energy efficient and have the further advantage that they come on instantly at full brightness, unlike CFLs, which can take a while to warm up. Advocates of LEDs note that the technology is versatile enough to work in almost any situation, from stadium lighting right down to the tiny light on your phone that flashes to indicate a new message. But not even LEDs, it seems, are the end of the story. Yet another lighting technology is on the horizon that offers further advantages: even greater power efficiency and softer, warmer light, the colour of which can be precisely controlled. Even though it will be put to rather mundane uses, the technology in question has an exotic name: quantum-dot lighting.”

Quantum dots will not supply the primary light source in bulbs containing them; rather, quantum dots change the color of the primary light source to achieve desired effects. That is why quantum dot technology adds to the cost of LED technology. The only way to make quantum dot lighting cheaper is to make LED lighting cheaper. The Economist continues:

“Quantum dots are tiny crystals of semiconducting material just a few tens of atoms, or a few nanometers (billionths of a meter), across. They are typically made using some combination of zinc, cadmium, selenium and sulphur atoms. Their origins go back to work published in 1983 by Louis Brus, then at Bell Labs, in New Jersey, though it was several years before another physicist, Mark Reed at Yale University, described these tiny semiconductor clumps as ‘quantum dots’. When excited by light or electricity, a quantum dot emits light of a color determined by the dot’s size and the material from which it is made. Light of a particular color can therefore be produced by exciting dots of a specific size.”

The article is accompanied by a video and full explanations of quantum dot technology:

“Seth Coe-Sullivan, co-founder and chief technology officer of QD Vision, a start-up spun out of the Massachusetts Institute of Technology, likens a quantum dot to a tuning fork: when it is struck, it oscillates at a specific, fixed frequency, producing a note of a particular pitch (or, in the case of a quantum dot, light of a particular color). This has immediate applications in general lighting, but quantum dots can also be put to many other uses. In lighting, quantum dots allow the color of the light from a light source to be precisely controlled, says Jason Hartlove, the chief executive of Nanosys, based in Palo Alto, California—one of a handful of companies making quantum dots and selling lighting components based on them. The first products to come to market use quantum dots to produce warm, white light from blue LEDs. In essence, quantum dots are used to change the color of the light. The advantage of this approach is that blue LEDs are the brightest, most energy-efficient kind. Existing white LEDs are also based on blue ones, the light from which is used to excite a phosphor layer made of yttrium aluminum garnet (YAG). The phosphor absorbs some of the blue light and is ‘pumped’ into an excited state. When it relaxes, the energy it has absorbed is re-emitted as yellowish light. The combination of blue and yellow produces a rough approximation of white light. But it contains less red light than is found in natural light, says Mr Hartlove. As a result, the light seems cold and harsh. The same is true of some kinds of fluorescent lighting, which are also deficient in red light. ‘The light is not very pleasing to the human eye,’ says Dr Coe-Sullivan.”

As noted in the BusinessWeek article cited above, targeted customers for initial sales of quantum dot lighting are commercial enterprises. The Economist article provides additional information:

“QD Vision’s first product, developed in conjunction with Nexxus Lighting of Charlotte, North Carolina, consists of a film embedded with quantum dots of different sizes in carefully chosen ratios. The film attaches to the front of a bulb containing several blue LEDs, and acts like a phosphor: blue light from the LEDs excites the quantum dots, causing them to emit light in a range of colors which combines to form white light. This approach has two advantages over using a YAG phosphor: with the right combination of quantum dots, the resulting light can be tuned to be much warmer; and quantum dots convert blue light to white light with an efficiency approaching 100%, so less energy is needed to produce a given amount of white light. The bulb (shown above) will go on sale this year. It will offer the performance of a 70-watt incandescent bulb but will draw only 11 watts. (A comparable CFL bulb would draw around 15 watts.)”

Just because QD Vision/Nexxus are targeting commercial customers it doesn’t mean that normal people won’t be holding quantum technology in their hands. That’s because Nanosys is targeting a different market — consumer products like cell phones, televisions, and computers.

“Nanosys is using a similar approach, coating blue LEDs with quantum dots to produce highly efficient white LEDs for use as backlights for the liquid-crystal displays (LCDs) used in computers, mobile phones and televisions. In January the company signed an agreement with the component-manufacturing arm of LG Electronics, which will use its products to produce backlights for mobile-phone displays. Nanosys calls this quantum-dot backlighting technology Quantum Rail (see picture above). It requires only about half as much energy as the conventional white LEDs used in backlights, which should help extend the battery life of mobile devices, as well as providing richer, more saturated colors.”

Although I noted earlier that quantum dots won’t provide the primary source of light in most situations, there are circumstances where they might. The Economist article explains:

“Stimulating quantum dots using light in order to get them to emit light of their own is called photoluminescence. Solutions of quantum dots in chloroform glow vividly when illuminated with ultraviolet light, turning light that is imperceptible to human eyes into bright colours. But quantum dots can also be made to glow using direct electrical stimulation—a phenomenon called electroluminescence. The problem is that this latter approach is currently much less energy-efficient, says Dr Coe-Sullivan. Provided this problem can be overcome, however, it should be possible to manufacture quantum dots in large, flexible sheets, opening up many new possibilities in lighting. The first electroluminescent products are likely to be light bulbs, which will probably be available from around 2012, he says. But the technology would also make possible glowing wallpaper that emits light directly, and could be used to make new kinds of signage and displays.”

Providing lighting in “large, flexible sheets” is an idea that has captivated designers. Even though light sheets using quantum dots may be a ways off, other technologies are being used such as flexible OLED lights. The Economist explains what OLED lights are:

“One type of emissive display that already exists is based on organic light-emitting diodes (OLEDs). These displays offer deep blacks and high contrast ratios (because no light is emitted from the display in black areas), and are lighter and thinner than LCDs. But the organic materials have a limited lifetime and the technology is expensive to scale up. As a result OLED displays are used in some mobile phones and small televisions, but they have not caught on widely. Researchers have already built experimental displays that combine quantum dots with the underpinnings of OLED displays. Such QD-LED displays may well dethrone LCDs as the dominant display technology in a decade or so. They would offer the benefits of OLED technology, including deep blacks and low power consumption, but with a much longer lifetime, says Mr Hartlove.”

Some designers aren’t willing to wait “a decade or so” and believe that OLED lighting will catch on [“Panels of Light Fascinate Designers,” by Eric A. Taub, New York Times, 6 September 2009]. Taub reports:

“LED light bulbs, with their minuscule energy consumption and 20-year life expectancy, have grabbed the consumer’s imagination. But an even newer technology is intriguing the world’s lighting designers: OLEDs, or organic light-emitting diodes, create long-lasting, highly efficient illumination in a wide range of colors, just like their inorganic LED cousins. But unlike LEDs, which provide points of light like standard incandescent bulbs, OLEDs create uniform, diffuse light across ultrathin sheets of material that eventually can even be made to be flexible. Ingo Maurer, who has designed chandeliers of shattered plates and light bulbs with bird wings, is using 10 OLED panels in a table lamp in the shape of a tree. The first of its kind, it sells for about $10,000. He is thinking of other uses. ‘If you make a wall divider with OLED panels, it can be extremely decorative. I would combine it with point light sources,’ he said. Other designers have thought about putting them in ceiling tiles or in Venetian blinds, so that after dusk a room looks as if sunshine is still streaming in.”

I’m not sure who is right about the lifespan of OLED lights. As noted above, The Economist states that “organic materials have a limited lifetime” while Taub claims that OLED lights “create long-lasting, highly efficient illumination.” The primary use for OLED technology continues to be in cellphones. Taub reports that in “2008, seven million of the one billion cellphones sold worldwide used OLED screens.” He goes on to report that in 2010, “that number will jump more than sevenfold, to 50 million phones.” Unlike The Economist, which doesn’t see much of future for OLED lighting, Taub believes that the lighting sector will be OLED’s “most promising market.” He explains:

“Within a year, manufacturers expect to sell the first OLED sheets that one day will illuminate large residential and commercial spaces. Eventually they will be as energy efficient and long-lasting as LED bulbs, they say. Because of the diffuse, even light that OLEDs emit, they will supplement, rather than replace, other energy-efficient technologies, like LED, compact fluorescent and advanced incandescent bulbs that create light from a single small point. Its use may be limited at first, designers say, and not just because of its high price. ‘OLED lighting is even and monotonous,’ said Mr. Maurer, a lighting designer with studios in Munich and New York. ‘It has no drama; it misses the spiritual side.’ ‘OLED lighting is almost unreal,’ said Hannes Koch, a founder of rAndom International in London, a product design firm. ‘It will change the quality of light in public and private spaces.’ Mr. Koch’s firm was recently commissioned by Philips to create a prototype wall of OLED light, whose sections light up in response to movement. Because OLED panels could be flexible, lighting companies are imagining sheets of lighting material wrapped around columns. (General Electric created an OLED-wrapped Christmas tree as an experiment.) OLED can also be incorporated into glass windows; nearly transparent when the light is off, the glass would become opaque when illuminated. Because OLED panels are just 0.07 of an inch thick and give off virtually no heat when lighted, one day architects will no longer need to leave space in ceilings for deep lighting fixtures, just as homeowners do not need a deep armoire for their television now that flat-panel TVs are common. The new technology is being developed by major lighting companies like G.E., Konica Minolta, Osram Sylvania, Philips and Universal Display.”

The truth about OLED’s future probably lies somewhere between The Economist‘s pessimism and Taub’s optimism. I believe that because one OLED proponent, Anil Duggal, a physical chemist at GE’s research labs in upstate New York, claims he has “had trouble selling his radical idea: Flexible, light-producing sheets that may soon outshine the bulb” [“Innovator: Anil Duggal,” by Rachel Layne, Bloomberg BusinessWeek, 24 June 2010]. Layne reports:

“The lightbulb, once a symbol of General Electric’s ingenuity, has shrunk to such a small percentage of its sales over the years that GE tried, unsuccessfully, to sell off the business in 2008. As it turns out, the Connecticut-based conglomerate has been directing a research effort at making the screw-in bulb obsolete. Anil Duggal … says he may be about a year away from producing durable and green lighting that is neither incandescent nor fluorescent. The technology is called organic light-emitting diodes (OLEDs, not to be confused with LEDs, a different technology), and it could revolutionize the way the world is lit. GE’s OLEDs will come in rolls of flexible sheets less than a tenth of an inch thick, and Duggal says their energy efficiency now matches compact fluorescents—with room for improvement. Their pliability opens the door to light-producing furniture, wallpaper (or ceilingpaper), and items that have yet to be imagined. Like GE co-founder Thomas Edison, who improved Humphry Davy’s lightbulb, Duggal is taking OLEDs, which have existed for decades, and focusing on how to mass-produce them.”

Layne notes that Duggal has been working on his ideas for over a decade and initially had a difficult time procuring funding to keep his project alive. Fortunately, he was able to secure a million-dollar grant from the U.S. Department of Energy back in the late 1990s. “Then in 2001, Jeff Immelt, still new in the role of CEO, challenged GE engineers and scientists to strive for breakthrough ideas. Today, OLED and LED research get about half of GE’s R&D budget for lighting.” She continues:

“All GE’s major rivals are working on OLEDs, but Duggal’s manufacturing process and his flexible product may prove to be a huge advantage for GE, says Frost & Sullivan analyst Abhigyan Sengupta. As a student, Duggal, 44, was torn between philosophy, religion, and the physical sciences. His drive to solve tangible problems won out: ‘My personal dream was to change the world … technology-wise.’ Before that happens, GE, Duggal—and the outside designers who will be given sheets of the stuff—must figure out how to turn this new material into products on store shelves.”

Both quantum dots and OLEDs remain in their infancies. But, as The Economist article concludes: “It is often said of new technologies that their future looks bright, but in the case of quantum dots [and OLEDs] that is no exaggeration—it is the literal truth.”