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Why blue LEDs are worth a Nobel Prize

October 09, 2014 13:12 IST

Blue light-emitting diodes help create the glowing screens of mobile phones, computers and TVs and promises to revolutionise the way the world lights its homes and offices.

Shivanand Kanavi reports on the importance of these little lights that won the Nobel Prize this year.

White and blue light emitting diodes used as Christmas decorations in Tokyo. Photograph: Toru Hanai/Reuters
 

That bluish-white light glowing from the screens of most new televisions, smartphones, laptops and tablet computers?

It comes from light-emitting diodes, better known as LEDs. Many businesses light their work spaces with LEDs. More and more, LEDs light up outdoor street signs and traffic lights.

Some homeowners have begun turning to this new form of lighting to illuminate their rooms. And most cars and trucks now use these same LEDs in their tail lights.

Three scientists have now won the 2014 Nobel Prize in physics for developing the technology that has made this lighting possible.

On Tuesday, October 7, three Japan-born scientists -- Isamu Akasaki, Hiroshi Amano and Shuji Nakamura -- won the Nobel Prize in physics for the invention of blue light-emitting diodes -- a new energy-efficient and environmentally friendly light source.

According to the Royal Swedish Academy of Sciences, the committee that bestows the honour, which includes a prize money of 8 million kronor (Rs 6.8 crore/Rs 68 million), when Nakamura, Akasaki and Amono 'produced bright blue light beams from their semiconductors in the early 1990s, they triggered a fundamental transformation of lighting technology.'

Explaining further, the committee said, 'The LED lamp holds great promise for increasing the quality of life for over 1.5 billion people around the world who lack access to electricity grids.'

The question now that arises is can semiconductor chips, which have revolutionised the way we live, give us light? The answer today is, it can.

Such chips for lighting are not made of silicon, which is used in electronics but more complex semiconductors, made of alloys of gallium, indium, arsenic, nitrogen, aluminum, phosphorous.

It has been known since the turn of the century that some semiconductors emit light when a current is passed through them. However, it has taken almost a hundred years for technology to do it efficiently and inexpensively.

The discovery and perfection of direct conversion of electricity into light has also led to the reverse that is the development of more efficient solar panels to convert light into electricity.

The first bright LEDs to be invented were emitting red, then orange and yellow light. However, attempts at producing green and blue LEDs were not very successful till a Japanese scientist Shuji Nakamura invented a bright blue LED and later white LED in the mid-1990s.

Nakamura's work brightened up the whole field and intense activity ensued leading to fast growth. He worked hard with very little funding and repeated disillusionment for several years to come up with blue LEDs.

The company he worked for at that time, Nichia is today one of the world leaders in blue and white LEDs and lasers. A few years ago, he moved out of Nichia and today, is a faculty member at the University of California at Santa Barbara.

LEDs for lighting purposes have many advantages. They convert electricity much more efficiently into light than say incandescent bulbs or fluorescent lamps. In fact, 90 per cent of energy in incandescent bulbs is wasted as heat.

LEDs also last much longer -- up to 1,00,000 hours -- that is more than 12 years of continuous operation. Whereas in the case of incandescent lamps, they last for 1,000 hours while fluorescent lamps last for 10,000 hours.

LEDs also consume less electricity, which is why batteries in a LED flashlight, for example, seem to go on forever. These make LEDs ideal if you are in a remote area on your own, camping or even in times of natural disaster.

However, LEDs do, like with all technology, have some flaws and weaknesses.

One the brightness of LEDs -- that is measured in Lumens per Watt of electrical power -- is still nowhere near the standard required for high brightness lighting. Secondly, the products are still expensive and lastly, the light is extremely bright in one direction hence, a LED light directed towards your work bench or a flashlight works well but if you try to light up your room with it then you end up using too many LEDs.

Image, Below: Isamu Akasaki, Hiroshi Amano and Shuji Nakamura, this year's Nobel Prize winners for Physics.

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Shivanand Kanavi
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