A walk through the lighting section of any hardware store, and you may be dazzled by not only the sparkling fixtures but also the sheer number of options with which you are presented.
A few of your choices include incandescent, fluorescent and LED lights. One of the most energy-efficient general lighting technologies – light-emitting diodes, or LEDs, use twenty-five to thirty percent of the energy of the halogen incandescents they replace. They are free of mercury, less prone to breakage, and boast a general life expectancy of fifty thousand hours – in other words – nearly fourteen years.
In the most simplified terms, an LED is a semiconductor device that emits light when an electrical current is passed through it. LEDs work on the principle of electroluminescence. This process can be described as a phenomenon in which a material emits light when an electrical current is passed through it.
The principle of electroluminescence was discovered in 1907 by Henry Joseph Round using silicone carbide and a so-called cat’s whisker detector (not actually made out of a cat’s whisker). The British inventor noticed that when voltage was applied to silicon carbide crystal, it emitted a dim yellow light. A more thorough investigation and proposed theory was later published by Russian scientist Oleg Vladimirovich Losev in his 1927 paper “Luminous Carborundum Detector and Detection Effect and Oscillations with Crystals”.
Many years passed before significant progress was made on light emitting diode research. It was not until 1962 that Gary Pittman and James Robert “Bob” Biard from Texas Instruments secured a patent for infrared LEDs. The first visible spectrum LED was developed by General Electric engineer Nick Holonyak, Jr.
In 1972, a former graduate student of Holonyak – M. George Craford – invented the first yellow LED and increased by ten-fold the brightness of red and red-orange LEDs. High brightness, high-efficiency LEDs were not created until 1976, when T.P. Pearsall designed them using his newly invented semiconductor materials. Shuji Nakamura of Nichia Corporation made the first blue LED in 1979 but it was too expensive for commercial use until 1994.
