A scientist whose project was deemed so hopeless that he had to pursue it in his spare time has won the 2014 Nobel prize in physics for an invention that paved the way for widespread energy-efficient lighting.
Shuji Nakamura, 60, at the University of California, Santa Barbara, shares the coveted prize – and 8m Swedish kronor (£690,000) – withIsamu Akasaki and Hiroshi Amano of Japan for “the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources.”
Speaking to the Royal Swedish Academy of Sciences, which woke him in California with a 3am phone call, Nakamura said over a crackling line that receiving the prize was “amazing” and “unbelieveable”. The three scientists will receive their award at a ceremony in Stockholm in December.
The invention of the blue LED transformed lighting. The devices can be used with a phosphor or combined with red and green LEDs to generate white light for illuminating homes and offices, traffic signals and huge advertising screens. They are so efficient that if the UK switched over to LED lighting, the nation could save 10% of its electricity bill and do without or eight new power stations, said Sir Colin Humphrey, director of research at Cambridge University.
“It’s so well deserved,” Humphrey told the Guardian. “Based on this bright blue LED you can make white LEDs and those are becoming widespread all over the world for solid state lighting. This is going to save lots of energy.” About a quarter of the world’s electricity is used for lighting.
Conventional lightbulbs are inefficient because they work by heating up a wire filament. The hot filament produces light, but wastes substantial amounts of energy through lost heat. Fluorescent lamps are better, but do not come close to the efficiency of white LEDs.
In an LED, light is produced when negative electrons combine with positive “holes” in wafer-thin layers of semiconductors. Red LEDs became widely available in the 1960s and adorned calculators and digital watches through the 1970s. Green LEDs were developed around the same time.
But despite these early successes, scientists failed for decades in their attempts to create blue LEDs. These were crucial though if white LED lighting was ever to become a reality: only blue light – which has the highest visible frequencies – can be converted into white light.
The stumbling block was that no one had a way to grow and modify crystals of a material called gallium nitride, which the laureates believed could be coaxed into producing blue light. In 1986, two of the prize winners, Akasaki, 85, at Meijo and Nagoya universities, and Amano, 54, at Nagoya University, cracked the problem by growing the material on sapphire coated with aluminium nitride. Six years and countless failed experiments later, they revealed their first LED that emitted bright blue light.
Nakamura, meanwhile, was working at a small Japanese firm called Nichia Corporation when he solved the same problem by growing the first layer of gallium nitride at a low temperature, and adding further layers at higher temperatures. He worked in his own time, because the task was considered as hopeless by his employer. In 1992, Nakamura made another major breakthrough that showed how gallium nitride layers could be modified to carry the positive holes needed to make blue LEDs work.
Nakamura’s efforts did not impress his bosses as much as they might have done. In 2001, he sued Nichia after they gave him just $200 for developing blue LEDs. Estimating that the invention was worth more than $500m (then £350m) to the company, a court ordered Nichia to pay him $200m. The firm appealed against the decision and Nakamura reluctantly accepted $8m in 2005.
“They didn’t approve of his work, they thought it was going nowhere. So he did his work in secret. He did his normal work in the daytime, then came back in the evening and worked all night. What he did was particularly remarkable,” said Humphreys.
White LED lights have benefits beyond improved efficiency. Unlike some energy-efficient lightbulbs, they come on instantly. They can survive 11 years of continuous use. Since the average lightbulb is on for four hours a day, an LED light could last for 60 years of normal use.
The three scientists went on to join forces to build a blue laser, which had at its heart a blue LED the size of a grain of sand. Because blue light has such a short wavelength, it can store far more information than other colours or infrared light. The increased storage capacity allowed by blue LEDs quickly led to the development of Blu-ray discs.
Donal Bradley, vice-provost for research at Imperial College London, said: “This took years of unrecognised effort – initially Shuji Nakamura’s work at the Nichia Chemical Company was classified as ‘under the table’ or ‘Friday afternoon’ research since it was considered so unpromising that it was not backed as an official research project.”
Frances Saunders, president of the UK Institute of Physics, said: “This is physics research that is having a direct impact on the grandest of scales, helping protect our environment, as well as turning up in our everyday electronic gadgets.”
