STOCKHOLM, Sweden (AP) — Two Japanese scientists and a Japanese-born American yesterday won the Nobel Prize in physics for inventing blue light-emitting diodes, a breakthrough that has spurred the development of LED technology to light up homes, computer screens and smartphones, worldwide.

Isamu Akasaki, Hiroshi Amano and naturalised US citizen Shuji Nakamura revolutionised lighting technology two decades ago when they came up with a long-elusive component of the white LED lights that in countless applications today have replaced less efficient incandescent and fluorescent lights.

“They succeeded where everyone else had failed,” the Nobel committee said. “Incandescent light bulbs lit the 20th century; the 21st century will be lit by LED lamps.”

LEDs contribute to saving the Earth’s resources because about one-fourth of world electricity consumption is used for lighting purposes. They tend to last 10 times longer than fluorescent lamps and 100 times longer than incandescent light bulbs.

“The blue LED is a fundamental invention that is rapidly changing the way we bring light to every corner of the home, the street and the workplace — a practical invention that comes from a fundamental understanding of physics in the solid state,” said H Frederick Dylla, the executive director and CEO of the American Institute of Physics.

LED technology holds particular promise in lighting up parts of the developing world with poor electricity grids, Nobel committee member Olga Botner said. Ultraviolet LEDs can also be used to sterilise water, she said.

“It is not just for lighting Christmas lights on the streets of Stockholm in December, but really something that benefits mankind, particularly the Third World,” she said.

Phillip Schewe, a physicist at the Joint Quantum Institute at the University of Maryland, said the prize shows that physics research can provide a practical benefit, rather than just probing the mysteries of the universe.

Nadarajah Narendran, director of research at the Lighting Research Center at the Rensselaer Polytechnic Institute in Troy, New York, estimated that about 10 per cent of illumination in US homes, offices, streets and industries comes from LED lights. Within five years, he said, that fraction will probably exceed 30 per cent as prices come down.

Red and green light-emitting diodes have been around since the mid-20th century and have been used in applications such as watches and calculators. But scientists had struggled for decades to produce the shorter-wavelength blue LED needed in combination with the others to produce white light when the three laureates made their breakthroughs in the early 1990s.

Their work enabled LED lights — more efficient and long-lasting than previous light sources — to be used in a range of applications, including street lights, televisions and computers.

“It is very satisfying to see that my dream of LED lighting has become a reality,” Nakamura, 60, said in a statement released by the University of California, Santa Barbara, where he is a professor. “I hope that energy-efficient LED light bulbs will help reduce energy use and lower the cost of lighting worldwide.”

Later, Nakamura was asked if he realised the importance of his research at the time.

“Nobody can make a cellphone without (blue) LED, my invention,” he responded.

Akasaki, an 85-year-old professor at Meijo University and Nagoya University, said in a nationally televised news conference in Japan that he had often been told that his research wouldn’t bear fruit.

“But I never felt that way,” he said. “I was just doing what I wanted to do.”

Akasaki and Amano, 54, made their inventions while working at Nagoya University, while Nakamura was working separately at Japanese company Nichia Chemicals. They built their own equipment and carried out thousands of experiments — many of which failed — before they made their breakthroughs.

Amano was on a plane and couldn’t be reached by the Nobel judges yesterday, said Jessica Balksjo Nannini, a spokeswoman for the Royal Academy of Sciences, which awards the physics prize.

On Monday, US-British scientist John O’Keefe split the Nobel Prize in medicine with Norwegian couple May-Britt Moser and Edvard Moser for breakthroughs in brain cell research that could pave the way for a better understanding of diseases like Alzheimer’s.

The Nobel award in chemistry will be announced today, followed by the literature award on Thursday, the Nobel Peace Prize on Friday, and the economics prize on Monday.

Worth 8 million kronor (US$1.1 million) each, the Nobel Prizes are always handed out on December 10, the anniversary of prize founder Alfred Nobel’s death in 1896. Besides the prize money, each laureate receives a diploma and a gold medal.