Physics Nobel honors energy-saving lightbulbs
This year the Nobel Committee decided to honor a physics discovery that benefits us all: lightbulbs. The 2014 Nobel Prize in physics went to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for their discovery of blue light-emitting diodes (LEDs), which have enabled modern energy-efficient light sources.
“Something like a fourth of our electricity consumption goes to illumination,” Nobel Prize committee member Olle Inganäs of Linköping University in Sweden said during a press conference Oct. 7 announcing the award. “Having much more light for much less electricity is really going to have a big impact.”
The new Nobel laureates worked for years to achieve blue LEDs, which, when combined with red and green LEDs, can create white light. The red and green versions have been around since the 1960s, but the blue took about another 30 years to accomplish. “A lot of big companies really tried to do this and they failed,” said Nobel committee member Per Delsing of Chalmers University of Technology in Sweden. “But these guys persisted and they tried and tried again and eventually they actually succeeded.”
The achievement required the growth of high-quality gallium nitride crystals, which are semiconductors. Inside semiconductors, electrons and “holes,” or spaces without electrons, can move around the crystal lattice to allow electrical current to flow. When the right voltage is applied to the semiconductor, electrons and holes will recombine and emit light. The wavelength of the light—the color—depends on the band gap, or the energy required to free an electron in the material. The band gap of gallium nitride allows it to create ultraviolet and blue light.
The white light sources enabled by the discovery of blue LEDs last much longer and require much less energy than traditional incandescent lightbulbs. Whereas incandescent bulbs use electricity to heat a metal filament, and therefore waste energy by releasing it in the form of not just light but heat, LEDs more efficiently convert energy directly into light, without the heat. LEDs also avoid pitfalls of other light sources, such as fluorescent lights, which rely on mercury. This technology now illuminates our smart phone screens and phone flashlights, as well as many household lights and even the twinkling lights put on Christmas trees. And because ultraviolet light kills bacteria, blue LEDs could potentially be used to sterilize water in the future, Delsing said. “I really think that Alfred Nobel would be very happy about this prize. He wanted his prize to be given for inventions that benefited mankind.”
Akasaki and Amano worked together at the University of Nagoya to make the discovery, and Nakamura worked independently at the Nichia Chemicals company in Tokushima, Japan. He is now a professor of engineering at the University of California, Santa Barbara. He learned of his award Tuesday just before 3 a.m. local time, and phoned into the press conference to describe the feeling of winning. “It’s unbelievable,” Nakamura said. “It’s amazing. Unbelievable.”
Akasaki was also informed by phone, but the Nobel Prize committee had not yet reached Amano when it made the announcement, because he happened to be flying from Japan to France. “I think actually they were not prepared for it,” said Staffan Normark, permanent secretary of the Royal Swedish Academy of Sciences. “They had not been waiting all day or all night for this call.”