Light Emitting Diodes (LEDs), “semiconductors that emit light when zapped with [positive polarity] electricity,”
[1]
are on the verge of taking over the commercial and consumer sectors of
the lighting industry. With greater efficiency, longer useful lives,
and their “clean” nature, LEDs are the future of light, pushing
traditional incandescent and fluorescent bulbs toward extinction. Only
the higher production costs for LEDs has extended the existence of
traditional bulbs.
History
When viewing the
history of traditional bulbs, the higher costs associated with producing
LEDs is not an insurmountable hurdle to overcome. The incandescent
bulb lingered for about 70 years before supplanting “candles, oil
lanterns, and gas lamps” as the main source of lighting.
[2] When
the first crude incandescent bulb was created in 1809 by Humphrey Davy,
an English chemist, using two charcoal strips to produce light, it
remained impractical. Later when the first true incandescent bulb was
created by Warren De la Rue in 1820, utilizing a platinum filament to
produce light, it was too expensive for commercial use. Only when
Thomas Edison created an incandescent bulb utilizing a carbonized
filament within a vacuum in 1879, did the incandescent bulb become
practical and affordable for consumer use.
Although considered
relatively novel, the concept for LEDs first arose in 1907 when Henry
Joseph Round used a piece of Silicone Carbide (SiC) to emit a dim,
yellow light. This was followed by experiments conducted by Bernhard
Gudden and Robert Wichard Pohl in Germany during the late 1920s, in
which they used “phosphor materials made from Zinc Sulphide (ZnS)
[treated] with Copper (Cu)” to produce dim light.
[3] However,
during this time, a major obstacle existed, in that many of these early
LEDs could not function efficiently at room temperature. Instead, they
needed to be submerged in liquid nitrogen (N) for optimal performance.
This
led to British and American experiments in the 1950s that used Gallium
Arsenide (GaAs) as a substitute for Zinc Sulphide (ZnS) and the creation
of an LED that produced invisible, infrared light at room temperature.
These LEDs immediately found use in photoelectric, sensing
applications. The first “visible spectrum” LED, producing “red” light
was created in 1962 by Nick Holonyak, Jr. (b. 1928) of the General
Electric Company who used Gallium Arsenide Phosphide (GaAsP) in place of
Gallium Arsenide (GaAs). Once in existence, they were quickly adopted
for use as indicator lights.
Before long these red LEDs were
producing brighter light and even orange-colored electroluminescence
when Gallium Phosphide (GaP) substrates were used. By the mid 1970s,
Gallium Phoshide (GaP) itself along with dual Gallium Phosphide (GaP)
substrates were being used to produce red, green, and yellow light.
This ushered in the trend “towards [LED use in] more practical
applications” such as calculators, digital watches and test equipment,
since these expanded colors addressed the fact that “the human eye is
most responsive to yellow-green light.”
[4]
However, rapid
growth in the LED industry did not begin until the 1980s when Gallium
Aluminium Arsenides (GaAIAs) were developed, providing “superbright”
LEDs (10x brighter than LEDs in use at the time) – “first in red, then
yellow and… green,” which also required less voltage providing energy
savings.
[5] This led to the concept of the first LED flashlight, in 1984.
Then
in parallel with emerging laser diode technology, which focused on
maximizing light output, the first “ultrabright” LEDs were created in
the early 1990s through the use of Indium Gallium Aluminium Phosphide
(InGaAIP) led in part by Toshiba’s creation of an LED that “reflected
90% or more of the generated light…” In addition, during this same
period, it was discovered that different colors, including “white”
(although a “true” white light was only recently produced through the
use of an organic LED (OLED) by Cambridge Display Technology, in the
U.K.) could be produced through “adjustments in the size of the energy
band gap” when Indium Gallium Aluminium Phosphide (InGaAIP) was used,
much in part because of the work of Shuji Nakamura of Nichia
Corporation, who developed the world’s first blue LED in 1993.
[6]
Today, this technology is used to produce LEDs that even emit
“exotic colors” such as pink, purple and aqua as well as “genuine
ultra-violet ‘black’ light.
[7]
A critical milestone was
reached in 1997 when it became cost effective to produce “high
brightness” LEDs in which the intensity (benefits) exceeded the
associated costs to produce it.
In conjunction with this milestone, newer technology is emerging
that will likely reduce costs even further (and improve lighting) – the
introduction of quantum dots or microscopic crystals ([8]
Advantages
The
advantages of adopting LEDs to provide sole source lighting for every
application are significant. LEDs emit virtually no heat (wasted
energy) and are “in fact… cool to the touch” unlike incandescent light
bulbs. They are also more durable (encased in a hardened shell and
resistant to vibration and shocks) than and last up to 50 times longer
than traditional incandescent and fluorescent bulbs ( some can be used
for up to 10 years), and they “use a greater proportion of the
electricity flowing through them” translating into “savings for
consumers.”
[9] According to the U.S. Department of Energy,
“widespread adoption of LEDs could cut U.S. consumption of electricity
for lighting by 29%”
[10] since they require less energy to
function and by their nature, reduce the amount of air conditioning
needed to keep areas cool and comfortable.
The shape of LEDs also
provides lighting benefits when compared to that of traditional bulbs.
Unlike incandescent and fluorescent bulbs, LEDs do not require the use
of an external reflector to collect and direct their light. In
addition, “LEDs light up very quickly… achiev[ing] full brightness in
approximately 0.01 seconds – 10 times faster than” traditional bulbs.
[11]
LEDs
also produce no ultra-violet output, which can damage fabrics, unlike
traditional bulbs; they are light-weight, ecologically friendly, and can
produce different colors (without the use of color filters) based on
the amount of power provided to each primary color ensuring that
electricity is not wasted. The Massachusetts Institute of Technology
(Nano Structures Lab) is presently conducting research that could lead
to the creation of an LED “where both color and intensity (brightness)
can be set electronically.”
[12]
Uses and the Future
As
LEDs gain a greater portion of the lighting market, they are currently
used in a variety of devices and applications ranging from traffic
control devices (e.g. traffic lights, which include the single signal
device that changes colors from green to yellow to red), barricade
lights, hazard signs, message displays (e.g. Times Square, New York,
commodities and news message boards, scoreboards), cellphones,
televisions, large video screens used at sporting and other outdoor
events (e.g. Miami Dolphins end-zone screen), calculators, digital
clocks and watches, flashlights (including models for which 60 seconds
of manual winding provides one-hour of light, eliminating the need to
stockpile fresh batteries for emergencies), Christmas lights, airport
runway lights, buoy lights, and automotive applications (e.g. indicator
lights as well as head lights and signal lights in some vehicles;
driver’s of the new 2006 Ford Mustang can even change the color (125
different varieties) of their “LED-laden dashboard by using the
‘MyColor’ feature”
[13]).
In fact the automotive industry
plans to replace all bulbs with LEDs by 2010, while efforts are
currently underway to replace all traffic signals with LED devices. At
the same time, plans are in place to eventually use LEDs to light
streets as well as much of the Third World and other areas “with no
means of electricity” since “solar charged batteries” can power LEDs for
the duration of each night.
[14]
In addition, “Phillips
Electronics is developing remote-controlled LED room lighting [while]
Boeing Corp. plans to use LED’s throughout the interior of its new 787
Dreamliner commercial jet.”
[15]
With the promise that LEDs
hold, it is likely that someday they will provide illumination for
houses and offices, X-Ray capabilities for the medical field, power
computer monitors, as well as an assortment of other devices and
applications. The possibilities are endless. However, before LEDs can
supplant the traditional bulb, “designers and advocates of the
technology must overcome… the usual obstacles to mainstream market
adoption: Industry-accepted standards must be developed and costs must
be reduced.”
[16] Currently costs are coming down and some
companies are moving towards these industry standards (e.g. Phillips
Electronics is working on LED bulbs that can screw into existing light
sockets, while besthomeledlighting.com already offers LED screwable
bulbs -- one consisting of 70 LEDS that emits a "warm white color
similar to the light from an incandescent bulb"
[17] using only 3
Watts of energy and another LED bulb that actually changes colors when
lit). With these efforts along with the adoption, exploitation, and
production of LED technology by growing numbers of companies, it is
inevitable that LEDs will become the sole source of lighting rendering
traditional incandescent and fluorescent bulbs extinct. In short, LEDs
are the light of the future, a light that will benefit not only
consumers but also industry and the Earth in general.
