Three scientists from Japan won the Nobel Prize for Physics on Tuesday for pioneering energy-efficient LED lighting, a weapon against global warming and poverty.

The trio are Isamu Akasaki, Hiroshi Amano and Shuji Nakamura, who has since become a US national.

"This year's Nobel Laureates are rewarded for having invented a new energy-efficient and environment-friendly light source -- the blue light-emitting diode (LED)," the jury said.

"Their inventions were revolutionary. Incandescent light bulbs lit the 20th century. The 21st century will be lit by LED lamps."

Red, green and blue need to be mixed to recreate the white light of the Sun.

Red and green diodes had been around for a long time, but devising a blue LED was the Holy Grail -- and achieving it took three long decades.

The breakthrough came in the 1990s when the three researchers, after dogged work, coaxed bright blue beams from semiconductors.

"They succeeded where everyone else had failed," the Nobel jury declared. "With the advent of LED lamps we now have more long-lasting and more efficient alternatives to older light sources."

LED lamps emit a bright light, last for tens of thousands of hours and use just a fraction of energy compared with the incandescent lightbulb pioneered by Thomas Edison in the 19th century.

The most advanced LED lamps now consume nearly 20 times less electricity than regular light bulbs and their performance is improving constantly.

LEDs are also commonplace in computers, TV, watches and mobile phone screens.

- Green benefit -

Around a quarter of world electricity consumption is used for lighting, so governments in many countries are promoting a switch to LEDs to slash emissions from fossil fuels.

And because they have very low electricity needs, LED lights can be connected to cheap, local solar power -- a benefit for the more than 1.5 billion people around the world without mains electricity.

"This technology has the potential to give lighting to these countries where there is no power grid," Nobel Committee member and atomic physicist Anne L'Huillier told AFP.

"This is really a new revolution in lighting technology. It's going to replace ordinary light bulbs and fluorescent tubes. Very soon there will only be these lamps."

Another committee member and physicist Per Delsing said the prize was in line with the wishes of Alfred Nobel, the Swedish inventor whose last testament stipulated the award should honour those who "have conferred the greatest benefit on mankind".

"I really think that Alfred Nobel would be happy with this prize... It's really something that will benefit most people," he said.

Nakamura was employed at Nichia Chemicals, a small Japanese company, when he carried out the research.

"I was happy and so surprised!" he told the Nobel Foundation by phone in the early hours of the morning in California.

"When I started my research I never expected I could invent an LED. I like research, it's like solving a quiz."

- 'Do whatever you like' -

His co-laureate Akasaki told reporters at Meijo University in Nagoya the announcement was "a half-surprise" and the "greatest honour".

"At first, it was said that this could not be invented during the 20th century. A lot of people left (the research project), but I never considered doing so at all," he said.

"I never thought of success or failure. I simply did what I wanted to do. Luckily, my colleagues supported me."

The octogenarian, born in 1929, had advice for young researchers: "Don't be fooled by fashionable subjects. Do whatever you like if it's really what you want to do."

The Nobel announcement was welcomed as "brilliant news" by the environmental group Greenpeace.

"It captures the spirit of the times," Sven Teske, a climate and energy campaigner, told AFP.

"It is high time that such innovative steps in the direction towards a sustainable future are celebrated and admired. Science and education are key to freeing us from fossil fuels."

Akasaki worked together with Amano at the University of Nagoya, when conducting their part of the path-breaking research.

He is currently a professor at Meijo University, while Amano, born in 1960, is a professor at Nagoya University. Nakamura, born in 1954 in Japan, is now a US citizen and a professor at University of California, Santa Barbara.

The winners will share the sum of eight million Swedish kronor ($1.1 million, 880,000 euros). The awards ceremony takes place in Stockholm on December 10.

Last year's physics Nobel went to Peter Higgs of Britain and Francois Englert of Belgium for the discovery of the Higgs boson, which gives mass to other elementary particles.