LEDs: The Light of the Future

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, Mini LED TV 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]).

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