Blue-light special: three scientists share Nobel for physics for work on LEDs
Three researchers, one from the United States and two from Japan, have been awarded the 2014 Nobel Prize in Physics for their roles in developing light-emitting diodes that shine blue – for decades, a Holy Grail in the field of photonics.
The trio's collective breakthroughs have spawned light bulbs that last for a decade and consume less than 20 percent of the power incandescent bulbs use to provide the same amount of light. Blue LEDs have made possible today's flat-panel, full-color computer monitors and TV screens, and are used in lasers for Blu-ray DVD players and higher density data storage on computer DVDs. The technology also is being incorporated into water purifiers, which use ultraviolet light to kill bacteria and viruses in water.
Globally, LED lights, combined with batteries and solar panels to charge them, could allow more than 1 billion people to move from kerosene lamps – or no lamps at all – to electric lighting without using local gas or diesel generators or regional power plants to provide it.
Unlike many Nobel Prizes, the rationale for this year's selection is relatively easy to grasp, notes Fredrick Dylla, executive director of the American Institute of Physics (AIP) in Washington.
People "can walk into a hardware store and see white LED lights that are still rather expensive, but have labels that say they won't burn out for 10 years and the cost of operating" is about one-tenth that of an incandescent bulb, he says, dubbing it lighting for the 21st century.
What's so big about blue? It was the last holdout on the path to using LEDs to provide white light. Blue, or more properly cyan, is one of three primary colors, along with magenta and yellow. In pigments for paint, which selectively reflect light, an equal blend of the three yields black. With light itself, however, an equal blend of the three yields white. In both cases, all of the other colors in the visible spectrum result from a judicious mix of the primary colors.
Between the end of World War II and the mid-1950s, researchers were uncovering the mechanism in semiconductors that allowed some of them to emit light when subjected to an electric current. The first LEDs out of the gate in the early 1960s operated at infrared wavelengths as well as red. In addition, yellow became common.
But for lighting, blue and green wouldn't emerge commercially until the mid-1990s. The first white LEDs started appearing in computer screens around the middle of the 2000s.
This year's winners – Isamu Akasaki, with Meijo University and Nagoya University, Hiroshi Amano, of Nagoya University, and Shuji Nakamura, with the University of California at Santa Barbara – are sharing the $1.1 million prize for "very carefully choosing materials" and the techniques for incorporating them into light-emitting diodes "into configurations that work, then work for a reasonable period of time, and at a reasonable brightness and efficiency," Dr. Dylla explains.
"This was a journey" 30 years in the making, not the culmination of a single eureka moment, he adds.
Indeed, the LED light bulbs on the market today have yet to realize the goal of blending light from red, blue, and green LEDs. Although the light from white LEDs is used directly in flashlights and some floodlights, the most cost-effective way of getting LED room lighting to market has been to harness the light from blue LEDs to tickle a layer of phosphor inside the bulb. The phosphor has been formulated to yield the right amount of red and green light as it glows to make white light when it combines with the light from the blue LED.
Red, green, and blue LEDs are used in computer displays and smart-phone screens, but these applications require sophisticated circuitry to control the production of the full range of colors, especially when the screen is displaying videos.
The three researchers will receive their award at a ceremony in Stockholm on Dec. 10.
