(Karen Livesey’s article from The ABC NEWS AUS on 04 October 2023.)
Old-fashioned incandescent light bulbs are highly
inefficient. Because they work by heating a wire until it glows, they waste a
lot of energy as heat. In fact, less than 10 per cent of the energy they
consume goes to producing light.
In the 1980s, scientists realised light emitting diodes, or LEDs — small electronic components that emit light of a specific colour — would make more efficient light sources. But there was a problem. Although red and green LEDs had been developed in the middle of the twentieth century, nobody knew how to make a blue LED.
LEDs are thin
sandwiches of materials that respond to electricity in a very particular way.
When an electron moves from one energy level to another inside the material, it
emits light of a specific colour. All three colours of light (red, green and
blue) would be needed to produce the kind of white light people want in their
homes and workplaces.
In the early
1990s, in the culmination of almost 30 years of work by many groups, the missing
blue LEDs were found. In 2014, Isamu Akasaki, Hiroshi Amano and Shuji Nakamura
received the physics Nobel for the discovery.
The layers of
material chosen to make up the sandwich, plus the quality of each layer, had to
be refined in order to make the first blue LED. Since the initial discovery,
materials scientists have continued to improve the design and manufacture to
make blue LEDs more efficient.
Lighting
accounts for up to 20 per cent of total electricity consumption. LEDs use
roughly one sixth as much energy as incandescent light bulbs. They also last
much longer, with a lifetime of around 25,000 hours.
Why A Blue LED Is Worth A Nobel Prize
Three scientists
have jointly earned the Nobel Prize in physics for their work on blue LEDs, or
light-emitting diodes. Why blue in particular? Well, blue was the last — and
most difficult — advance required to create white LED light. And with white LED
light, companies are able to create smartphone and computer screens, as well as
light bulbs that last longer and use less electricity than any bulb invented
before.
LEDs are
basically semiconductors that have been built so they emit light when they’re
activated. Different chemicals give different LEDs their colors. Engineers made
the first LEDs in the 1950s and 60s. Early iterations included laser-emitting
devices that worked only when bathed in liquid nitrogen. At the time,
scientists developed LEDs that emitted everything from infrared light to green
light… but they couldn’t quite get to blue. That required chemicals, including
carefully-created crystals, that they weren’t yet able to make in the lab.
Once they did
figure it out, however, the results were remarkable. A modern white LED
lightblub converts more than 50 percent of the electricity it uses into light.
Compare that to the 4 percent conversion rate for incandescent bulbs, and you
have one efficient bulb.
Besides saving
money and electricity for all users, white LEDs’ efficiency makes them
appealing for getting lighting to folks living in regions without electricity
supply. A solar installation can charge an LED lamp to last a long time,
allowing kids to do homework at night and small businesses to continue working
after dark.
A modern white
LED lightblub converts more than 50 percent of the electricity it uses into
light. Compare that to the 4 percent conversion rate for incandescent bulbs.
LEDs also last
up to 100,000 hours, compared to 10,000 hours for fluorescent lights and 1,000
hours for incandescent bulbs. Switching more houses and buildings over to LEDs
could significantly reduce the world’s electricity and materials consumption
for lighting.
A white LED
light is easy to make from a blue one. Engineers use a blue LED to excite some
kind of fluorescent chemical in the bulb. That converts the blue light to white
light.
Two of this
year’s prize winners, Isamu Akasaki and Hiroshi Amano, worked together on
producing high-quality gallium nitride, a chemical that appears in many of the
layers in a blue LED. The previous red and green LEDs used gallium phosphide,
which was easier to produce. Akasaki and Amano discovered how to add chemicals
to gallium nitride semiconductors in such a way that they would emit light
efficiently. The pair built structures with layers of gallium nitride alloys.
The third
prize-winner, Shuji Nakamura, also worked on making high-quality gallium
nitride. He figured out why gallium nitride semiconductors treated with certain
chemicals glow. He built his own gallium nitride alloy-based structures.
Both Nakamura’s
and Akasaki’s groups will continue to work on making even more efficient blue
LEDs, the committee for the Nobel Prize in physics said in a statement.
Nakamura is now a professor at the University of California, Santa Barbara,
although he began his LED research at a small Japanese chemical company called
Nichia Chemical Corporation. Akasaki and Amano are professors at Nagoya
University in Japan.
In the future,
engineers may make white LEDs by combining red, green, and blue ones, which
would make a light with tunable colors, the Nobel Committee wrote.
Press release (Nobel Prize) on 7 October 2014
The Royal
Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for
2014 to Isamu Akasaki (Meijo
University, Nagoya, Japan and Nagoya University, Japan) and Hiroshi Amano (Nagoya University, Japan)
and Shuji Nakamura (University of
California, Santa Barbara, CA, USA) “for the invention of efficient blue
light-emitting diodes which has enabled bright and energy-saving white light
sources”
New light to
illuminate the world: 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). In the spirit of Alfred Nobel the Prize
rewards an invention of greatest benefit to mankind; using blue LEDs, white
light can be created in a new way. With the advent of LED lamps we now have
more long-lasting and more efficient alternatives to older light sources.
When Isamu
Akasaki, Hiroshi Amano and Shuji Nakamura produced bright blue light beams from
their semi-conductors in the early 1990s, they triggered a fundamental
transformation of lighting technology. Red and green diodes had been around for
a long time but without blue light, white lamps could not be created. Despite
considerable efforts, both in the scientific community and in industry, the
blue LED had remained a challenge for three decades.
They succeeded where everyone else had failed.
Akasaki worked together with Amano at the University of Nagoya, while Nakamura
was employed at Nichia Chemicals, a small company in Tokushima. Their
inventions were revolutionary. Incandescent light bulbs lit the 20th century;
the 21st century will be lit by LED lamps.
 |
| Professor Shuji Nakamura |
White LED lamps emit a bright white light, are long-lasting and energy-efficient. They are constantly improved, getting more efficient with higher luminous flux (measured in lumen) per unit electrical input power (measured in watt). The most recent record is just over 300 lm/W, which can be compared to 16 for regular light bulbs and close to 70 for fluorescent lamps.
As about one
fourth of world electricity consumption is used for lighting purposes, the LEDs
contribute to saving the Earth’s resources. Materials consumption is also
diminished as LEDs last up to 100,000 hours, compared to 1,000 for incandescent
bulbs and 10,000 hours for fluorescent lights.
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: due to low power
requirements it can be powered by cheap local solar power.
The invention of
the efficient blue LED is just twenty years old, but it has already contributed
to create white light in an entirely new manner to the benefit of us all. Prize
amount: SEK 8 million, to be shared equally between the Laureates.
