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rewarded himwith a bonus of $180. He quit, moved to the University of California,
Santa Barbara, and sued them. In 2005, Nichia settled and paid him $9 million.
Nakamura followed up with the development of the blue laser, now used in
Blu-Ray discs where the high frequency permits greater information density and
higher quality video discs.The combination of red, green and blue produces white
light.Work immediately began on developing white LEDs and the first commercial
versions were released in about 2005. Consider that 20-30% of our electricity
consumption is for lighting, and that white LEDs consume a tenth of the energy
of current lighting, and you can appreciate the impact it will have.
However, solid-state lighting can be used in a variety of applications, from full-
colour displays to motor vehicles and industrial lighting.
One current area of research is increasing the band gap further to produce
ultraviolet light that can be used for low-energy sterilisation for water purification
and commercial sterilisation systems. Another is continuing the development of
white light production at ever lower cost.
Organic LED developments are based on using a thin film of organic compounds
which emit light in response to current. The OLED can be based on polymer
layers, or on small molecules. OLED displays work without a backlight and so
are able to produce proper black and white colours, as well as being thinner and
lighter than LCDs.
These polymer displays have a different origin to LED research and light emission
was originally produced by a single layer. More recent developments have created
emissive and conductive layers sandwiched between a cathode and an anode,
equivalent p-n bilayers, with a band gap between the two organic semiconductors.
While efficient and low-cost white lights have not been produced just yet, colour
displays are now widely used in mobile display devices, like phones and tablets.
Research into efficient solid-state lighting continues with the focus on lowering
costs of production while improving colour rendering and raising the power output.
One of the more interesting is that of the quantum dot, a nanocrystal made
of doped semiconductor which is small enough to exhibit quantum mechanical
properties. It is being considered in a wide range of applications, including for
medical imaging, solar cells, and qubits in quantum computing.
Besides the higher resolution that quantum dots offer for displays, white light
emission is created by using a blue LED as a light-source and converting part of
the emitted light into green and red light by placing quantum dots in front of the
blue light. This has the potential to produce very efficient displays.
The same approach will produce white light for more traditional applications.
As the technology improves, costs are falling. A US government assessment
declares that, since 2008, prices for LED white lights have fallen 85% while the
installed base has grown from 400 000 LED lights to over 20 million.
This includes use the motor industry where LEDs are used in everything from
headlights and brake lights to internal displays. The same report estimates that
this has saved about $675 million a year in energy costs.
Consider how much lighting is managed by the state – from street lighting to
traffic signals to their own office buildings – and you can see that it doesn’t need
widespread adoption by individuals to kick start the industry. Governments just
need to recognise the savings they can make on their energy bills and drive their
own change to stimulate the industry.
In South Africa, with the incredible pressure on Eskom’s generating capacity,
replacing every incandescent lamp would help reduce in the incidence of ‘load
shedding’.
Consider that the Medupi Power Station is to cost R170 billion while adding
4800 MW of power to our existing supply of 44 000 MW. R170 billion to add only
about 12% to our capacity.
R170 billion would buy over 10 million street lights and put LEDs into every
home in the country. That would save at least 20% of our energy demand. The
equivalent of two Medupis.
The dedication of Isamu Akasaki, Hiroshi Amano and Shuji Nakamura has
granted us a tremendous opportunity and has the potential to improve our lives
in almost infinite ways.
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LiD
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