The LED revolution and why its discoverers deserve the Nobel

Nobel Media

This week the Nobel Prize for Physics was awarded to Isamu Akasaki and Hiroshi Amano of Japan and Japanese-born U.S. citizen Shuji Nakamura for their discovery of the blue light emitting diode. Here's why it was so richly deserved.

A good way to appreciate the significance of the blue light emitting diode (LED) is to imagine what difference it would make if it had never been invented. If all we cared about was blue light for its own sake, the answer would be “not much”.

The reason why blue light is important is that when combined with red and green it is possible to generate millions of colours, including white. Remember the colour wheel, now think about an LED television. To produce the brilliantly coloured images, every one of the millions of pixels is made up of tiny red, green and blue LEDs. By varying the intensity of the individual LEDs millions of different colours can be generated, including white.

Not only are the colours from the LED television more vibrant than alternatives, they are also generated by a very efficient process.

But a Nobel prize for helping to make a better television is also a stretch. Much more importantly, the blue LED has allowed a revolution in lighting for our homes, factories and streets that is underpinning massive reductions in carbon dioxide emissions, measurably improving the sustainability of our planet.

To create the modern white lights that are replacing conventional, fluorescent and halogen light globes, a blue LED or its close relative, an ultraviolet LED, illuminates a phosphor coating that converts the single-colour emitted by the LED into the broad spectrum of colours in white light.

The best of these LED lights are now many times more efficient than halogens and conventional incandescents, slightly more efficient than fluorescents, and still improving. LED light emission is based on subatomic effects in the semiconductor material of which they are made rather than heating up a tungsten filament to thousands of degrees temperature until it glows white hot.

Today’s white-light LEDs emit about 90 lumens of light per watt, corresponding to 13% efficiency converting electricity into light, much better than the approximately 3% efficiency of a tungsten-filament conventional light source.

LEDs are transforming lighting in every field, using less electricity to produce better light, thereby mitigating many millions of tons of carbon dioxide emissions. It cannot be long before most other forms of lighting become obsolete.

You can read Alan Finkel's column, The Incurable Engineer, here.

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